Issue: If you notice any inconsistencies between this Grid Layout Module
and the Flexible Box Layout Module,
please report them to the CSSWG,
as this is likely an error.
Introduction
This section is not normative.
Grid Layout is a new layout model for CSS
that has powerful abilities to control the sizing and positioning of boxes and their contents.
Unlike Flexible Box Layout, which is single-axis–oriented,
Grid Layout is optimized for 2-dimensional layouts:
those in which alignment of content is desired in both dimensions.
Representative Flex Layout ExampleRepresentative Grid Layout Example
In addition, due to its ability to explicitly position items in the grid,
Grid Layout allows dramatic transformations in visual layout structure
without requiring corresponding markup changes.
By combining media queries with the CSS properties that control layout of the grid container and its children,
authors can adapt their layout to changes in device form factors, orientation, and available space,
while preserving a more ideal semantic structuring of their content
across presentations.
Although many layouts can be expressed with either Grid or Flexbox,
they each have their specialties.
Grid enforces 2-dimensional alignment,
uses a top-down approach to layout,
allows explicit overlapping of items,
and has more powerful spanning capabilities.
Flexbox focuses on space distribution within an axis,
uses a simpler bottom-up approach to layout,
can use a content-size–based line-wrapping system to control its secondary axis,
and relies on the underlying markup hierarchy
to build more complex layouts.
It is expected that both will be valuable
and complementary tools for CSS authors.
Background and Motivation
Application layout example requiring horizontal and vertical alignment.
As websites evolved from simple documents into complex, interactive applications,
techniques for document layout, e.g. floats,
were not necessarily well suited for application layout.
By using a combination of tables, JavaScript, or careful measurements on floated elements,
authors discovered workarounds to achieve desired layouts.
Layouts that adapted to the available space were often brittle
and resulted in counter-intuitive behavior as space became constrained.
As an alternative, authors of many web applications opted for a fixed layout
that cannot take advantage of changes in the available rendering space on a screen.
The capabilities of grid layout address these problems.
It provides a mechanism for authors to divide available space for layout into columns and rows
using a set of predictable sizing behaviors.
Authors can then precisely position and size the building block elements of their application
into the grid areas defined by the intersections of these columns and rows.
The following examples illustrate the adaptive capabilities of grid layout,
and how it allows a cleaner separation of content and style.
Adapting Layouts to Available Space
Five grid items arranged according to content size and available space.Growth in the grid due to an increase in available space.
Grid layout can be used to intelligently resize elements within a webpage.
The adjacent figures represent a game with five major components in the layout:
the game title, stats area, game board, score area, and control area.
The author's intent is to divide the space for the game such that:
The stats area always appears immediately under the game title.
The game board appears to the right of the stats and title.
The top of the game title and the game board should always align.
The bottom of the game board and bottom of the stats area align when the game has reached its minimum height.
In all other cases the game board will stretch to take advantage of all the space available to it.
The controls are centered under the game board.
The top of the score area is aligned to the top of the controls area.
The score area is beneath the stats area.
The score area is aligned to the controls beneath the stats area.
The following grid layout example shows how an author might achieve
all the sizing, placement, and alignment rules declaratively.
/**
* Define the space for each grid item by declaring the grid
* on the grid container.
*/
#grid {
/**
* Two columns:
* 1. the first sized to content,
* 2. the second receives the remaining space
* (but is never smaller than the minimum size of the board
* or the game controls, which occupy this column [Figure 4])
*
* Three rows:
* 3. the first sized to content,
* 4. the middle row receives the remaining space
* (but is never smaller than the minimum height
* of the board or stats areas)
* 5. the last sized to content.
*/
display: grid;
grid-template-columns:
/* 1 */ auto
/* 2 */ 1fr;
grid-template-rows:
/* 3 */ auto
/* 4 */ 1fr
/* 5 */ auto;
}
/* Specify the position of each grid item using coordinates on
* the 'grid-row' and 'grid-column' properties of each grid item.
*/
#title { grid-column: 1; grid-row: 1; }
#score { grid-column: 1; grid-row: 3; }
#stats { grid-column: 1; grid-row: 2; align-self: start; }
#board { grid-column: 2; grid-row: 1 / span 2; }
#controls { grid-column: 2; grid-row: 3; justify-self: center; }
Note: There are multiple ways to specify the structure of the grid
and to position and size grid items,
each optimized for different scenarios.
Source-Order Independence
An arrangement suitable for “portrait” orientation.An arrangement suitable for “landscape“ orientation.
Continuing the prior example,
the author also wants the game to adapt to different devices.
Also, the game should optimize the placement of the components when viewed either in portrait or landscape orientation (Figures 6 and 7).
By combining grid layout with media queries,
the author is able to use the same semantic markup,
but rearrange the layout of elements independent of their source order,
to achieve the desired layout in both orientations.
The following example uses grid layout’s ability to name the space which will be occupied by a grid item.
This allows the author to avoid rewriting rules for grid items
as the grid’s definition changes.
@media (orientation: portrait) {
#grid {
display: grid;
/* The rows, columns and areas of the grid are defined visually
* using the grid-template-areas property. Each string is a row,
* and each word an area. The number of words in a string
* determines the number of columns. Note the number of words
* in each string must be identical. */
grid-template-areas: "title stats"
"score stats"
"board board"
"ctrls ctrls";
/* The way to size columns and rows can be assigned with the
* grid-template-columns and grid-template-rows properties. */
grid-template-columns: auto 1fr;
grid-template-rows: auto auto 1fr auto;
}
}
@media (orientation: landscape) {
#grid {
display: grid;
/* Again the template property defines areas of the same name,
* but this time positioned differently to better suit a
* landscape orientation. */
grid-template-areas: "title board"
"stats board"
"score ctrls";
grid-template-columns: auto 1fr;
grid-template-rows: auto 1fr auto;
}
}
/* The grid-area property places a grid item into a named
* area of the grid. */
#title { grid-area: title }
#score { grid-area: score }
#stats { grid-area: stats }
#board { grid-area: board }
#controls { grid-area: ctrls }
Note: The reordering capabilities of grid layout intentionally affect
only the visual rendering,
leaving speech order and navigation based on the source order.
This allows authors to manipulate the visual presentation
while leaving the source order intact and optimized for non-CSS UAs
and for linear models such as speech and sequential navigation.
Advisement: Grid item placement and reordering must not be used
as a substitute for correct source ordering,
as that can ruin the accessibility of the document.
Value Definitions
This specification follows the CSS property definition conventions from [[!CSS2]]
using the value definition syntax from [[!CSS-VALUES-3]].
Value types not defined in this specification are defined in CSS Values & Units [[!CSS-VALUES-3]].
Combination with other CSS modules may expand the definitions of these value types.
In addition to the property-specific values listed in their definitions,
all properties defined in this specification
also accept the CSS-wide keywords as their property value.
For readability they have not been repeated explicitly.
Overview
This section is not normative.
Grid Layout controls the layout of its content
through the use of a grid:
an intersecting set of horizontal and vertical lines
which create a sizing and positioning coordinate system
for the grid container’s contents.
Grid Layout features
fixed, flexible, and content-based [[#track-sizing|track sizing functions]]
[[#placement|explicit item placement]] via forwards (positive) and backwards (negative) numerical grid coordinates,
named grid lines, and named grid areas;
automatic item placement into empty areas, including reordering with order
space-sensitive track repetition
and
automatic addition of rows or columns to accommodate additional content
The tracks (rows and columns) of the grid
are declared and sized
either explicitly through the explicit grid properties
or are implicitly created when items are placed outside the explicit grid.
The 'grid' shorthand and its sub-properties define the parameters
of the grid.
[[#grid-definition]]
Below are some examples of grid declarations:
The following declares a grid with four named areas:
H, A, B,
and F.
The first column is sized to fit its contents (''grid-template-columns/auto''),
and the second column takes up the remaining space (1fr).
Rows default to ''grid-template-rows/auto'' (content-based) sizing;
the last row is given a fixed size of ''30px''.
main {
grid: "H H "
"A B "
"F F " 30px
/ auto 1fr;
}
The following declares a grid with as many rows of at least ''5em''
as will fit in the height of the grid container (''100vh'').
The grid has no explicit columns;
instead columns are added as content is added,
the resulting column widths are equalized (1fr).
Since content overflowing to the right won't print,
an alternate layout for printing adds rows instead.
The following declares a grid with 5 evenly-sized columns
and three rows,
with the middle row taking up all remaining space
(and at least enough to fit its contents).
main {
grid: auto 1fr auto / repeat(5, 1fr);
min-height: 100vh;
}
Placing Items
The contents of the grid container are organized into individual grid items
(analogous to flex items),
which are then assigned to predefined [=grid areas|areas=] in the grid.
They can be explicitly placed using coordinates through the grid-placement properties
or implicitly placed into empty areas using [=auto-placement=].
[[#placement]]
Below are some examples of grid placement declarations
using the 'grid-area' shorthand:
grid-area: a; /* Place into named grid area “a” */
grid-area: auto; /* Auto-place into next empty area */
grid-area: 2 / 4; /* Place into row 2, column 4 */
grid-area: 1 / 3 / -1; /* Place into column 3, span all rows */
grid-area: header-start / sidebar-start / footer-end / sidebar-end;
/* Place using named lines */
These are equivalent to the following 'grid-row' + 'grid-column' declarations:
Once the grid items have been [[#placement|placed]],
the sizes of the grid tracks (rows and columns) are calculated,
accounting for the sizes of their contents and/or available space as specified in the grid definition.
The resulting sized grid is [[#grid-align|aligned]] within the grid container
according to the grid container’s 'align-content' and 'justify-content' properties.
[[#alignment]]
The following example justifies all columns
by distributing any extra space among them,
and centers the grid in the grid container
when it is smaller than 100vh.
In grid layout,
the content of a grid container is laid out
by positioning and aligning it into a grid.
The grid is an intersecting set of horizontal and vertical grid lines
that divides the grid container’s space into grid areas,
into which grid items (representing the grid container’s content) can be placed.
There are two sets of grid lines:
one set defining columns
that run along the block axis,
and an orthogonal set defining rows
along the inline axis.
[[!CSS3-WRITING-MODES]]
Grid lines: Three in the block axis and four in the inline axis.
Grid Lines
Grid lines are the horizontal and vertical dividing lines of the grid.
A grid line exists on either side of a column or row.
They can be referred to by numerical index,
or by an author-specified name.
A grid item references the grid lines to determine its position within the grid
using the [[#placement|grid-placement properties]].
The following two examples both create three column grid lines and four row grid lines.
This first example demonstrates how an author would position a grid item using grid line numbers:
This second example uses explicitly named grid lines:
/* equivalent layout to the prior example, but using named lines */
#grid {
display: grid;
grid-template-columns: 150px [item1-start] 1fr [item1-end];
grid-template-rows: [item1-start] 50px 1fr 50px [item1-end];
}
#item1 {
grid-column: item1-start / item1-end;
grid-row: item1-start / item1-end;
}
Grid Tracks and Cells
Grid track is a generic term for a grid column or grid row—in
other words, it is the space between two adjacent grid lines.
Each grid track is assigned a sizing function,
which controls how wide or tall the column or row may grow,
and thus how far apart its bounding grid lines are.
Adjacent grid tracks can be separated by [[#gutters|gutters]]
but are otherwise packed tightly.
A grid cell is the intersection of a grid row and a grid column.
It is the smallest unit of the grid that can be referenced when positioning grid items.
In the following example there are two columns and three rows.
The first column is fixed at 150px.
The second column uses flexible sizing, which is a function of the unassigned space in the grid,
and thus will vary as the width of the grid container changes.
If the used width of the grid container is 200px, then the second column is 50px wide.
If the used width of the grid container is 100px, then the second column is 0px
and any content positioned in the column will overflow the grid container.
#grid {
display: grid;
grid-template-columns: 150px 1fr; /* two columns */
grid-template-rows: 50px 1fr 50px; /* three rows */
}
Grid Areas
A grid area is the logical space used to lay out one or more grid items.
A grid area consists of one or more adjacent grid cells.
It is bound by four grid lines, one on each side of the grid area,
and participates in the sizing of the grid tracks it intersects.
A grid area can be named explicitly using the 'grid-template-areas' property of the grid container,
or referenced implicitly by its bounding grid lines.
A grid item is assigned to a grid area
using the [[#placement|grid-placement properties]].
/* using the template syntax */
#grid {
display: grid;
grid-template-areas: ". a"
"b a"
". a";
grid-template-columns: 150px 1fr;
grid-template-rows: 50px 1fr 50px;
}
#item1 { grid-area: a }
#item2 { grid-area: b }
#item3 { grid-area: b }
/* Align items 2 and 3 at different points in the grid area "b". */
/* By default, grid items are stretched to fit their grid area */
/* and these items would layer one over the other. */
#item2 { align-self: start; }
#item3 { justify-self: end; align-self: end; }
A grid item’s grid area forms the containing block into which it is laid out.
Grid items placed into the same grid area do not directly affect each other's layout.
Indirectly, however, a grid item occupying a grid track with an intrinsic sizing function
can affect the size of that track (and thus the positions of its bounding grid lines),
which in turn can affect the position or size of another grid item.
Reordering and Accessibility
Grid layout gives authors great powers of rearrangement over the document.
However, these are not a substitute for correct ordering of the document source.
The 'order' property and grid placementdo not affect ordering in non-visual media
(such as speech).
Likewise, rearranging grid items visually does not affect
the default traversal order of sequential navigation modes
(such as cycling through links, see e.g. tabindex [[HTML]]).
Advisement:
Authors must use 'order' and the grid-placement properties
only for visual, not logical, reordering of content.
Style sheets that use these features to perform logical reordering are non-conforming.
Note: This is so that non-visual media and non-CSS UAs,
which typically present content linearly,
can rely on a logical source order,
while grid layout’s placement and ordering features are used to tailor the visual arrangement.
(Since visual perception is two-dimensional and non-linear,
the desired visual order is not always equivalent to the desired reading order.)
Many web pages have a similar shape in the markup,
with a header on top,
a footer on bottom,
and then a content area and one or two additional columns in the middle.
Generally,
it's desirable that the content come first in the page's source code,
before the additional columns.
However, this makes many common designs,
such as simply having the additional columns on the left and the content area on the right,
difficult to achieve.
This has been addressed in many ways over the years,
often going by the name "Holy Grail Layout" when there are two additional columns.
Grid Layout makes this example trivial.
For example, take the following sketch of a page's code and desired layout:
This layout can be easily achieved with grid layout:
body { display: grid;
grid: "h h h"
"a b c"
"f f f";
grid-template-columns: auto 1fr 20%; }
article { grid-area: b; min-width: 12em; }
nav { grid-area: a; /* auto min-width */ }
aside { grid-area: c; min-width: 12em; }
As an added bonus,
the columns will all be equal-height by default,
and the main content will be as wide as necessary to fill the screen.
Additionally,
this can then be combined with media queries to switch to an all-vertical layout on narrow screens:
@media all and (max-width: 60em) {
/* Too narrow to support three columns */
main { display: block; }
}
In order to preserve the author's intended ordering in all presentation modes,
authoring tools—including WYSIWYG editors as well as Web-based authoring aids--
must reorder the underlying document source
and not use 'order' or grid-placement properties to perform reordering
unless the author has explicitly indicated that the underlying
document order (which determines speech and navigation order) should be
out-of-sync with the visual order.
For example, a tool might offer both drag-and-drop arrangement of grid items
as well as handling of media queries for alternate layouts per screen size range.
Since most of the time, reordering should affect all screen ranges
as well as navigation and speech order,
the tool would match the resulting drag-and-drop visual arrangement
by simultaneously reordering the DOM layer.
In some cases, however, the author may want different visual arrangements per screen size.
The tool could offer this functionality
by using the grid-placement properties together with media queries,
but also tie the smallest screen size's arrangement to the underlying DOM order
(since this is most likely to be a logical linear presentation order)
while using grid-placement properties
to rearrange the visual presentation in other size ranges.
This tool would be conformant, whereas a tool that only ever used
the grid-placement properties
to handle drag-and-drop grid rearrangement
(however convenient it might be to implement it that way)
would be non-conformant.
Grid Containers
Establishing Grid Containers: the ''display/grid'' and ''inline-grid'' 'display' values
A grid container establishes
an [=independent formatting context|independent=] grid formatting context
for its contents.
This is the same as establishing an independent [=block formatting context=],
except that grid layout is used instead of block layout:
floats do not intrude into the grid container,
and the grid container's margins do not collapse with the margins of its contents.
The contents of a grid container are laid out into a grid,
with grid lines forming the boundaries of each grid items’ containing block.
Grid containers are not block containers,
and so some properties that were designed with the assumption of block layout
don't apply in the context of grid layout.
In particular:
'float' and 'clear' have no effect on a grid item.
However, the 'float' property still affects the computed value of 'display' on children of a grid container,
as this occurs beforegrid items are determined.
'vertical-align' has no effect on a grid item.
the ''::first-line'' and ''::first-letter'' pseudo-elements do not apply to grid containers,
and grid containers do not contribute a first formatted line or first letter to their ancestors.
If an element's specified 'display' is ''inline-grid''
and the element is floated or absolutely positioned,
the computed value of 'display' is grid.
The table in CSS 2.1 Chapter 9.7 is thus amended
to contain an additional row,
with ''inline-grid'' in the "Specified Value" column
and ''grid'' in the "Computed Value" column.
Sizing Grid Containers
Note see [[!CSS-SIZING-3]] for a definition of the terms in this section.
A grid container is sized
using the rules of the formatting context in which it participates:
Since memory is limited,
UAs may clamp the possible size of the implicit grid
to be within a UA-defined limit
(which should accommodate lines at in the range [-10000, 10000]),
dropping all lines outside that limit.
If a grid item is placed outside this limit,
its grid area must be clamped to within this limited grid.
To clamp a grid area:
* If the grid area would span outside the limited grid,
its span is clamped to the last line of the limited grid.
* If the grid area would be placed completely outside the limited grid,
its span must be truncated to 1
and the area repositioned into the last grid track on that side of the grid.
For example, if a UA only supported grids with at most 1000 tracks in each dimension,
the following placement properties:
Loosely speaking, the grid items of a grid container
are boxes representing its in-flow contents.
Each in-flow child of a grid container
becomes a grid item,
and each contiguous sequence of child text runs
is wrapped in an anonymousblock containergrid item.
However, if the entire sequence of child text runs contains only
white space
(i.e. characters that can be affected by the 'white-space' property)
it is instead not rendered (just as if its text nodes were ''display:none'').
Note: inter-element white space disappears:
it does not become its own grid item,
even though inter-element text does get wrapped in an anonymous grid item.
Note: The box of a anonymous item is unstyleable,
since there is no element to assign style rules to.
Its contents will however inherit styles (such as font settings) from the grid container.
Grid Item Display
A grid item [=establishes an independent formatting context=] for its contents.
However, grid items are grid-level boxes, not block-level boxes:
they participate in their container's grid formatting context,
not in a block formatting context.
If the [=computed value|computed=] 'display' value of an element's nearest ancestor element
(skipping ''display:contents'' ancestors)
is ''grid'' or ''inline-grid'',
the element's own 'display' value is [=blockified=].
(See CSS2.1§9.7 [[!CSS2]]
and [[css-display-3#transformations]]
for details on this type of 'display' value conversion.)
Note: Blockification still occurs even when the ''grid'' or ''inline-grid'' element does not end up generating a [=grid container=] box,
e.g. when it is [=replaced element|replaced=]
or in a ''display: none'' subtree.
Note: Some values of 'display' normally trigger the creation of anonymous boxes around the original box.
If such a box is a grid item,
it is blockified first,
and so anonymous box creation will not happen.
For example, two contiguous grid items with ''display: table-cell''
will become two separate ''display: block'' grid items,
instead of being wrapped into a single anonymous table.
Grid Item Sizing
A grid item is sized within the containing block defined by its grid area.
Grid item calculations for 'auto' widths and heights
vary by their [[css-align-3#self-alignment|self-alignment values]]:
: ''align-self/normal''
::
If the grid item is a [=replaced element=] with an intrinsic size in the relevant dimension
(or with an aspect ratio and an intrinsic size in the other dimension)
the grid item is sized as for ''align-self: start''
(consistent with the width calculation rules for block-level replaced elements in [[CSS2/visudet#block-replaced-width]]).
Otherwise,
if the grid item has a [=preferred aspect ratio=],
the grid item is sized as for a [=block-level box=].
Otherwise,
the grid item is sized as for ''align-self/stretch''.
: ''align-self/stretch''
::
Use the [=inline size=] calculation rules for non-replaced boxes
(defined in [[CSS2/visudet#blockwidth]]).
Note: This can distort the aspect ratio of the item, if it has one.
: all other values
:: Size the item as ''width/fit-content''.
The following informative table summarizes the automatic sizing of grid items:
Summary of automatic sizing behavior of grid items
Alignment
Non-replaced Element Size
Replaced Element Size
''align-self/normal''
Fill grid area
Use intrinsic size
''align-self/stretch''
Fill grid area
Fill grid area
''align-self/start''/''align-self/center''/etc.
''width/fit-content'' sizing (like floats)
Use intrinsic size
Note: The ''min-width/auto'' value of 'min-width' and 'min-height'
affects track sizing in the relevant axis
similar to how it affects the main size of a flex item.
See [[#min-size-auto]].
Reordered Grid Items: the 'order' property
The 'order' property also applies to grid items.
It affects their [[#grid-auto-flow-property|auto-placement]] and [[#z-order|painting order]].
Advisement: As with reordering flex items,
the 'order' property must only be used
when the visual order needs to be out-of-sync
with the speech and navigation order;
otherwise the underlying document source should be reordered instead.
See [[css-flexbox-1#order-accessibility]]
in [[CSS-FLEXBOX-1]].
Grid Item Margins and Paddings
As adjacent grid items are independently contained
within the containing block formed by their grid areas,
the margins of adjacent grid items do not
collapse.
Percentage margins and paddings on grid items,
like those on block boxes,
are resolved against the inline size of their containing block,
e.g. left/right/top/bottom percentages
all resolve against their containing block’s width
in horizontal writing modes.
Auto margins expand to absorb extra space in the corresponding dimension,
and can therefore be used for alignment.
See [[#auto-margins]]
Z-axis Ordering: the 'z-index' property
Grid items can overlap when they are positioned into intersecting grid areas,
or even when positioned in non-intersecting areas because of negative margins or positioning.
The painting order of grid items is exactly the same as inline blocks [[CSS2]],
except that order-modified document order is used in place of raw document order,
and 'z-index' values other than auto create a stacking context even if 'position' is ''static''
(behaving exactly as if 'position' were ''relative'').
Thus the 'z-index' property can easily be used to control the z-axis order of grid items.
Note: Descendants that are positioned outside a grid item still participate in any stacking context established by the grid item.
The following diagram shows several overlapping grid items,
with a combination of implicit source order
and explicit 'z-index'
used to control their stacking order.
Drawing order controlled by z-index and source order.
If the item’s [=preferred size=] in the relevant axis is definite,
then the specified size suggestion is that size.
It is otherwise undefined.
transferred size suggestion
If the item has a [=preferred aspect ratio=]
and its [=preferred size=] in the opposite axis is definite,
then the transferred size suggestion is that size
(clamped by the opposite-axis [=minimum size|minimum=] and [=maximum sizes=] if they are definite),
converted through the aspect ratio.
It is otherwise undefined.
content size suggestion
The content size suggestion is
the min-content size in the relevant axis,
clamped, if it has a [=preferred aspect ratio=],
by any definite opposite-axis [=minimum size|minimum=] and [=maximum sizes=]
converted through the aspect ratio.
For the purpose of calculating an intrinsic size of the box
(e.g. the box’s min-content size),
a content-based minimum size causes the box’s size in that axis to become indefinite
(even if e.g. its 'width' property specifies a definite size).
Note this means that percentages calculated against this size
will [=behave as auto=].
Nonetheless, although this may require an additional layout pass to re-resolve percentages in some cases,
this value
(like the ''min-content'', ''max-content'', and ''fit-content'' values defined in [[CSS-SIZING-3]])
does not prevent the resolution of percentage sizes within the item.
Note that while a content-based minimum size is often appropriate,
and helps prevent content from overlapping or spilling outside its container,
in some cases it is not:
In particular, if grid layout is being used for a major content area of a document,
it is better to set an explicit font-relative minimum width such as ''min-width: 12em''.
A content-based minimum width could result in a large table or large image
stretching the size of the entire content area, potentially into an overflow zone,
and thereby making lines of text needlessly long and hard to read.
Note also, when content-based sizing is used on an item with large amounts of content,
the layout engine must traverse all of this content before finding its minimum size,
whereas if the author sets an explicit minimum, this is not necessary.
(For items with small amounts of content, however,
this traversal is trivial and therefore not a performance concern.)
Defining the Grid
The Explicit Grid
The three properties 'grid-template-rows', 'grid-template-columns', and 'grid-template-areas'
together define the explicit grid of a grid container
by specifying its explicit grid tracks.
The final grid may end up larger due to grid items placed outside the explicit grid;
in this case implicit tracks will be created,
these implicit tracks will be sized by the 'grid-auto-rows' and 'grid-auto-columns' properties.
The size of the explicit grid is determined by the larger of
the number of rows/columns defined by 'grid-template-areas'
and the number of rows/columns sized by 'grid-template-rows'/'grid-template-columns'.
Any rows/columns defined by 'grid-template-areas' but not sized by 'grid-template-rows'/'grid-template-columns'
take their size from the 'grid-auto-rows'/'grid-auto-columns' properties.
If these properties don't define anyexplicit tracks
the explicit grid still contains one grid line in each axis.
Numeric indexes in the grid-placement properties
count from the edges of the explicit grid.
Positive indexes count from the start side
(starting from 1 for the start-most explicit line),
while negative indexes count from the end side
(starting from -1 for the end-most explicit line).
The 'grid' and 'grid-template' properties are shorthands
that can be used to set all three explicit grid properties
('grid-template-rows', 'grid-template-columns', and 'grid-template-areas')
at the same time.
The 'grid' shorthand also resets properties controlling the implicit grid,
whereas the 'grid-template' property leaves them unchanged.
Explicit Track Sizing: the 'grid-template-rows' and 'grid-template-columns' properties
Name: grid-template-columns, grid-template-rows
Value: none | <> | <>
Initial: none
Applies to: grid containers
Inherited: no
Percentages: refer to corresponding dimension of the content area
Computed value: the keyword ''grid-template-columns/none'' or a [=computed track list=]
Animation type: if the list lengths match, by computed value type per item in the [=computed track list=] (see [[#computed-tracks]] and [[#repeat-interpolation]]); discrete otherwise
These properties specify,
as a space-separated track list,
the line names and track sizing functions of the grid.
The 'grid-template-columns' property specifies the track list for the grid's columns,
while 'grid-template-rows' specifies the track list for the grid's rows.
Values have the following meanings:
none
Indicates that no explicit grid tracks are created by this property
(though explicit grid tracks could still be created by 'grid-template-areas').
Note: In the absence of an explicit grid any rows/columns will be [[#implicit-grids|implicitly generated]],
and their size will be determined by the 'grid-auto-rows' and 'grid-auto-columns' properties.
<> | <>
Specifies the track list as a series of track sizing functions
and line names.
Each track sizing function can be specified as a length,
a percentage of the grid container’s size,
a measurement of the contents occupying the column or row,
or a fraction of the free space in the grid.
It can also be specified as a range using the ''minmax()'' notation,
which can combine any of the previously mentioned mechanisms
to specify separate min
and max track sizing functions for the column or row.
Where the component values are defined as follows…
Track Sizes
<>
A non-negative length or percentage, as defined by CSS3 Values. [[!CSS-VALUES-3]]
<> values are relative to
the innerinline size
of the grid container in column grid tracks,
and the innerblock size
of the grid container in row grid tracks.
If the size of the grid container
depends on the size of its tracks,
then the <>
must be treated as auto,
for the purpose of calculating the intrinsic sizes of the grid container
and then resolve against that resulting grid container size
for the purpose of laying out the grid and its items.
<>
A non-negative dimension with the unit ''fr'' specifying the track's flex factor.
Each <>-sized track takes a share of the remaining space in proportion to its flex factor.
For example, given a track listing of ''1fr 2fr'',
the tracks will take up ⅓ and ⅔ of the leftover space, respectively.
See [[#fr-unit]] for more details.
Note: If the sum of the flex factors is less than 1,
they'll take up only a corresponding fraction of the leftover space,
rather than expanding to fill the entire thing.
When appearing outside a ''minmax()'' notation,
implies an automatic minimum (i.e. ''minmax(auto, <>)'').
minmax(min, max)
Defines a size range
greater than or equal to min
and less than or equal to max.
If the max is less than the min,
then the max will be floored by the min
(essentially yielding ''minmax(min, min)'').
As a maximum, a <> value sets the track's flex factor;
it is invalid as a minimum.
Note: A future level of this spec may allow <> minimums,
and will update the track sizing algorithm to account for this correctly
auto
As a maximum: represents the largest max-content contribution
of the grid items occupying the grid track;
however, unlike ''max-content'',
allows expansion of the track
by the 'align-content' and 'justify-content' properties.
As a minimum: represents the largest minimum size
(specified by 'min-width'/'min-height')
of the grid items occupying the grid track.
(This initially is often, but not always,
equal to a ''min-content'' minimum--
see [[#min-size-auto]].)
When appearing outside a ''minmax()'' notation:
equivalent to ''minmax(auto, auto)'',
representing the range between
the minimum and maximum described above.
(This behaves similar to ''minmax(min-content, max-content)'' in the most basic cases,
but with extra abilities.)
Represents the formula
max(minimum, min(limit, ''max-content'')),
where minimum represents an ''grid-template-columns/auto'' minimum
(which is often, but not always, equal to a ''min-content'' minimum),
and limit is the track sizing function
passed as an argument to ''fit-content()''.
This is essentially calculated as the smaller of
''minmax(auto, max-content)'' and ''minmax(auto, limit)''.
Given the following 'grid-template-columns' declaration:
A distance from the previous line equal to half the free space
(the width of the grid container, minus the width of the non-flexible grid tracks).
A distance from the previous line equal to the maximum size of any grid items
belonging to the column between these two lines.
A distance from the previous line at least as large as the largest minimum size of any grid items
belonging to the column between these two lines,
but no larger than the other half of the free space.
If the non-flexible sizes
(''100px'', ''max-content'', and ''min-content'')
sum to larger than the grid container’s width,
the final grid line will be a distance equal to their sum away from the start edge of the grid container
(the ''1fr'' sizes both resolve to ''0'').
If the sum is less than the grid container’s width,
the final grid line will be exactly at the end edge of the grid container.
This is true in general whenever there's at least one <> value among the grid track sizes.
Additional examples of valid grid track definitions:
Note: The size of the grid is not purely the sum of the track sizes,
as 'row-gap', 'column-gap' and 'justify-content', 'align-content'
can add additional space between tracks.
Naming Grid Lines: the [<>*] syntax
While grid lines can always be referred to by their numerical index,
line names
can make the grid-placement properties easier to understand and maintain.
[=Line names=] can be explicitly assigned with the 'grid-template-rows' and 'grid-template-columns' properties,
or [=implicitly-assigned line name|implicitly assigned=] by named grid areas with the 'grid-template-areas' property.
For example,
the following code gives meaningful names to all of the lines in the grid.
Note that some of the lines have multiple names.
A line name cannot be span or auto,
i.e. the <> in the <> production
excludes the keywords span and auto.
Repeating Rows and Columns: the ''repeat()'' notation
The repeat() notation represents a repeated fragment of the track list,
allowing a large number of columns or rows that exhibit a recurring pattern
to be written in a more compact form.
This example shows two equivalent ways of writing the same grid definition.
Both declarations produce four “main” columns, each 250px wide,
surrounded by 10px “gutter” columns.
The generic form of the ''repeat()'' syntax is, approximately,
repeat( [ <> | auto-fill | auto-fit ] , <> )
The first argument specifies the number of repetitions.
The second argument is a track list,
which is repeated that number of times.
However, there are some restrictions:
* The ''repeat()'' notation can’t be nested.
* Automatic repetitions (''auto-fill'' or ''auto-fit'')
cannot be combined with
intrinsic
or flexible sizes.
Thus the precise syntax of the ''repeat()'' notation
has several forms:
* The <> variant can represent the repetition of any <>,
but is limited to a fixed number of repetitions.
* The <> variant can repeat automatically to fill a space,
but requires definite track sizes so that the number of repetitions can be calculated.
It can only appear once in the track list,
but the same track list can also contain <>s.
If a ''repeat()'' function
ends up placing two <> adjacent to each other,
the name lists are merged.
For example, ''repeat(2, [a] 1fr [b])'' is equivalent to ''[a] 1fr [b a] 1fr [b]''.
Repeat-to-fill: ''auto-fill'' and ''auto-fit'' repetitions
When auto-fill is given as the repetition number,
if the grid container has a definite size or max size in the relevant axis,
then the number of repetitions is the largest possible positive integer
that does not cause the grid to overflow
the content box of its grid container
(treating each track as its max track sizing function if that is definite
or as its minimum track sizing function otherwise,
flooring the max track sizing function by the min track sizing function if both are definite,
and taking 'gap' into account);
if any number of repetitions would overflow,
then 1 repetition.
Otherwise, if the grid container has a definite min size in the relevant axis,
the number of repetitions is the smallest possible positive integer that fulfills that minimum requirement.
Otherwise, the specified track list repeats only once.
For example, the following code will create
as many 25-character columns as will fit into the window width.
If there is any remaining space,
it will be distributed among the 25-character columns.
body {
display: grid;
grid-template-columns: repeat(auto-fill, minmax(25ch, 1fr));
}
The auto-fit keyword behaves the same as ''auto-fill'',
except that after [[#auto-placement-algo|grid item placement]]
any empty repeated tracks are collapsed.
An empty track is one with no in-flow grid items placed into or spanning across it.
(This can result in all tracks being collapsed,
if they're all empty.)
A collapsed track is treated as having
a fixed track sizing function of ''0px'',
and the gutters on either side of it--
including any space allotted through distributed alignment--
collapse.
For the purpose of finding the number of auto-repeated tracks,
the UA must floor the track size to a UA-specified value
to avoid division by zero.
It is suggested that this floor be ''1px''.
Interpolation/Combination of ''repeat()''
If two ''repeat()'' notations that
have the same first argument (repetition count)
and the same number of tracks in their second argument (the track listing),
they are combined by
combining each component of their computed track listsby computed value
(just like combining a top-level track list).
They otherwise combine discretely.
Flexible Lengths: the ''fr'' unit
A flexible length or <> is a dimension
with the fr unit,
which represents a fraction of the leftover space in the grid container.
Tracks sized with ''fr'' units are called flexible tracks
as they flex in response to leftover space
similar to how flex items with a zero base size fill space in a flex container.
The distribution of leftover space occurs after all non-flexible track sizing functions have reached their maximum.
The total size of such rows or columns is subtracted from the available space, yielding the leftover space,
which is then divided among the flex-sized rows and columns in proportion to their flex factor.
Each column or row's share of the leftover space can be computed as the column or row's
<flex> * <leftover space> / <sum of all flex factors>.
<> values between 0fr and 1fr have a somewhat special behavior:
when the sum of the flex factors is less than 1,
they will take up less than 100% of the leftover space.
A track’s <> value
is effectively a request for some proportion of the leftover space,
with ''1fr'' meaning “100% of the leftover space”;
then if the tracks in that axis are requesting more than 100% in total,
the requests are rebalanced to keep the same ratio but use up exactly 100% of it.
However, if the tracks request less than the full amount
(such as three tracks that are each ''.25fr'')
then they'll each get exactly what they request
(25% of the leftover space to each,
with the final 25% left unfilled).
See [[#algo-flex-tracks]] for the exact details
of how leftover space is distributed.
This pattern is required for continuous behavior as ''fr'' values approach zero
(which means the tracks wants none of the leftover space).
Without this, a ''1fr'' track would take all of the leftover space;
but so would a ''0.1fr'' track,
and a ''0.01fr'' track,
etc.,
until finally the value is small enough to underflow to zero
and the track suddenly takes up none of the leftover space.
With this behavior,
the track instead gradually takes less of the leftover space
as its flex factor shrinks below ''1fr'',
smoothly transitioning to taking none of the leftover space at zero.
Unless this “partial fill” behavior is specifically what's desired,
authors should stick to values ≥ 1;
for example, using ''1fr'' and ''2fr'' is usually better
than using ''.33fr'' and ''.67fr'',
as they're more likely to behave as intended
if tracks are added or removed.
When the available space is infinite
(which happens when the grid container’s width or height is indefinite),
flex-sized grid tracks are sized to their contents while retaining their respective proportions.
The used size of each flex-sized grid track is computed by
determining the ''max-content'' size of each flex-sized grid track
and dividing that size by the respective flex factor
to determine a “hypothetical ''1fr'' size”.
The maximum of those is used as the resolved ''1fr'' length (the flex fraction),
which is then multiplied by each grid track’s flex factor to determine its final size.
Note: <> values are not <>s
(nor are they compatible with <>s, like some <> values),
so they cannot be represented in or combined with other unit types in ''calc()'' expressions.
Computed Value of a Track Listing
A computed track list
is a list
alternating between [=line name sets=] and [=track sections=],
with the first and last items being [=line name sets=].
A line name set is a (potentially empty) set
of identifiers representing line names.
A track section is either:
* a ''minmax()'' functional notation representing a single track's size,
with each <> computed
* a ''repeat()'' functional notation representing a repeated track list section,
with its <> computed
and its <> represented as a [=computed track list=]
Resolved Value of a Track Listing
The 'grid-template-rows' and 'grid-template-columns' properties are
resolved value special case properties. [[!CSSOM]]
When an element generates a [=grid container=] box,
the resolved value
of its 'grid-template-rows' or 'grid-template-columns' property
is the used value,
serialized with:
Every track listed individually,
whether implicitly or explicitly created,
without using the ''repeat()'' notation.
Every track size given as a length in pixels,
regardless of sizing function.
Adjacent line names collapsed into a single bracketed set.
The first bullet point of the above list
means that implicit tracks get serialized
as part of 'grid-template-rows'/etc.,
despite the fact that an author cannot
actually specify implicit track sizes in those properties!
So 'grid-template-rows' and 'grid-template-columns' values
might not round-trip correctly:
const s = getComputedStyle(gridEl);
gridEl.style.gridTemplateRows = s.gridTemplateRows;
// Code like this should be a no-op,
// but if there are any implicit rows,
// this will convert them into explicit rows,
// possibly changing how grid items are positioned
// and altering the overall size of the grid!
This is an accidental property of an early implementation
that leaked into later implementations
without much thought given to it.
We intend to remove it from the spec,
but not until after we've defined a CSSOM API
for getting information about implicit tracks,
as currently this is the only way to get that information
and a number of pages rely on that.
Otherwise, (e.g. when the element has ''display: none'' or is not a grid container)
the resolved value is simply the computed value.
Note: In general, resolved values are the computed values,
except for a small list of legacy 2.1 properties.
However, compatibility with early implementations of this module
requires us to define 'grid-template-rows' and 'grid-template-columns' as returning used values.
ISSUE: The CSS Working Group is considering whether to also return used values
for the grid-placement properties
and is looking for feedback, especially from implementors.
See discussion.
Named Areas: the 'grid-template-areas' property
Name: grid-template-areas
Value: none | <>+
Initial: none
Applies to: grid containers
Inherited: no
Percentages: n/a
Computed value: the keyword ''grid-template-areas/none'' or a list of string values
Animation type: discrete
This property specifies named grid areas,
which are not associated with any particular grid item,
but can be referenced from the grid-placement properties.
The syntax of the 'grid-template-areas' property also provides a visualization
of the structure of the grid,
making the overall layout of the grid container easier to understand.
Values have the following meanings:
none
Indicates that no named grid areas,
and likewise no explicit grid tracks,
are defined by this property
(though explicit grid tracks could still be created by 'grid-template-columns' or 'grid-template-rows').
Note: In the absence of an explicit grid any rows/columns will be [[#implicit-grids|implicitly generated]],
and their size will be determined by the 'grid-auto-rows' and 'grid-auto-columns' properties.
<>+
A row is created for every separate string listed for the 'grid-template-areas' property,
and a column is created for each cell in the string,
when parsed as follows:
Tokenize the string into a list of the following tokens,
using longest-match semantics:
A sequence of name code points,
representing a named cell token
with a name consisting of its code points.
A sequence of one or more "." (U+002E FULL STOP),
representing a null cell token.
A sequence of whitespace,
representing nothing
(do not produce a token).
A sequence of any other characters,
representing a trash token.
Note: These rules can produce cell names that do not match the <> syntax,
such as "1st 2nd 3rd",
which requires escaping when referencing those areas by name in other properties,
like ''grid-row: \31st;'' to reference the area named ''1st''.
A trash token is a syntax error,
and makes the declaration invalid.
All strings must define the same number of cell tokens
([=named cell tokens=] and/or [=null cell tokens=]),
and at least one cell token,
or else the declaration is invalid.
If a named grid area spans multiple grid cells,
but those cells do not form a single filled-in rectangle,
the declaration is invalid.
Note: Non-rectangular or disconnected regions may be permitted in a future version of this module.
In this example, the 'grid-template-areas' property is used to create a page layout
where areas are defined for header content (head),
navigational content (nav),
footer content (foot),
and main content (main).
Accordingly, the template creates three rows and two columns,
with four named grid areas.
The head area spans both columns and the first row of the grid.
When serializing either the [=specified value|specified=] or [=computed value=] of a <> value of 'grid-template-areas',
each [=null cell token=] is serialized as a single "." (U+002E FULL STOP),
and consecutive cell tokens are separated by a single space (U+0020 SPACE),
with all other white space elided.
Implicitly-Assigned Line Names
The 'grid-template-areas' property generates implicitly-assigned line names from the named grid areas in the template.
For each named grid areafoo, four implicitly-assigned line names are created:
two named foo-start, naming the row-start and column-start lines of the named grid area,
and two named foo-end, naming the row-end and column-end lines of the named grid area.
These [=implicitly-assigned line names=] behave just like any other [=line names=],
except that they do not appear in the value of 'grid-template-rows'/'grid-template-columns'.
Even if an [=explicitly-assigned line name=] with the same name is defined,
the [=implicitly-assigned line names=] are just more lines with the same name.
Implicitly-Named Areas
Since a named grid area is referenced by the implicitly-assigned line names it produces,
explicitly adding named lines of the same form (''foo-start''/''foo-end'')
effectively creates a named grid area.
Such implicitly-named areas do not appear in the value of 'grid-template-areas',
but can still be referenced by the grid-placement properties.
Explicit Grid Shorthand: the 'grid-template' property
The 'grid-template' property is a shorthand for setting
'grid-template-columns', 'grid-template-rows', and 'grid-template-areas' in a single declaration.
It has several distinct syntax forms:
none
Sets all three properties to their initial values (''grid-template-rows/none'').
Sets 'grid-template-rows' and 'grid-template-columns' to the specified values, respectively,
and sets 'grid-template-areas' to ''grid-template-areas/none''.
grid-template: auto 1fr / auto 1fr auto;
is equivalent to
grid-template-rows: auto 1fr;
grid-template-columns: auto 1fr auto;
grid-template-areas: none;
[ <>? <> <>? <>? ]+ [ / <> ]?
* Sets 'grid-template-areas' to the strings listed.
* Sets 'grid-template-rows' to the <>s following each string
(filling in ''grid-template-rows/auto'' for any missing sizes),
and splicing in the named lines defined before/after each size.
* Sets 'grid-template-columns' to the track listing specified after the slash
(or ''grid-template-columns/none'', if not specified).
This syntax allows the author to align track names and sizes inline with their respective grid areas.
grid-template: [header-top] "a a a" [header-bottom]
[main-top] "b b b" 1fr [main-bottom]
/ auto 1fr auto;
is equivalent to
grid-template-areas: "a a a"
"b b b";
grid-template-rows: [header-top] auto [header-bottom main-top] 1fr [main-bottom];
grid-template-columns: auto 1fr auto;
and creates the following grid:
The grid created by the declarations above.
(The “a/b-start/end” names are [=implicitly-assigned line name|implicitly assigned=] by the named grid areas.)
Note: Note that the ''repeat()'' function isn't allowed in these track listings,
as the tracks are intended to visually line up one-to-one with the rows/columns in the “ASCII art”.
Note: The 'grid' shorthand accepts the same syntax,
but also resets the implicit grid properties to their initial values.
Unless authors want those to cascade in separately,
it is therefore recommended to use 'grid' instead of 'grid-template'.
The Implicit Grid
The 'grid-template-rows', 'grid-template-columns', and 'grid-template-areas' properties define a fixed number
of tracks that form the explicit grid.
When grid items are positioned outside of these bounds,
the grid container generates
implicit grid tracks
by adding implicit grid lines to the grid.
These lines together with the explicit grid form the implicit grid.
The 'grid-auto-rows' and 'grid-auto-columns' properties size these [=implicit grid tracks=],
as well as any [=explicit grid tracks=] created by 'grid-template-areas'
but not explicitly sized by 'grid-template-rows' or 'grid-template-columns'
The 'grid-auto-flow' property controls auto-placement of grid items
without an explicit position.
Once the explicit grid is filled
(or if there is no explicit grid)
auto-placement will also cause the generation of implicit grid tracks.
The 'grid' shorthand property can set the implicit grid properties
('grid-auto-flow', 'grid-auto-rows', and 'grid-auto-columns')
together with the explicit grid properties
in a single declaration.
Implicit Track Sizing: the 'grid-auto-rows' and 'grid-auto-columns' properties
Name: grid-auto-columns, grid-auto-rows
Value: <>+
Initial: auto
Applies to: grid containers
Inherited: no
Percentages: see [[#track-sizing|Track Sizing]]
Computed value: see [[#track-sizing|Track Sizing]]
Animation type: by computed value type
The 'grid-auto-columns' and 'grid-auto-rows' properties specify
the size of tracks not assigned a size
by 'grid-template-rows' or 'grid-template-columns'.
If multiple track sizes are given, the pattern is repeated as necessary
to find the size of the affected tracks.
The first track after the last explicitly-sized track
receives the first specified size, and so on forwards;
and the last implicit grid track before the explicit grid
receives the last specified size, and so on backwards.
Note: If a grid item is positioned into a row or column that is not explicitly declared
by 'grid-template-rows'/'grid-template-columns' and/or 'grid-template-areas',
[=implicit grid tracks=] are created to hold it.
This can happen either by explicitly positioning into a row or column that is out of range,
or by the [=auto-placement algorithm=] creating additional rows or columns.
A 2×2 grid with one explicit 20px×20px grid cell
in the first row+column
and three additional cells resulting from the implicit 40px column and row
generated to hold the additional grid items.
Automatic Placement: the 'grid-auto-flow' property
Grid items that aren't explicitly placed are automatically placed
into an unoccupied space in the grid container
by the auto-placement algorithm.
'grid-auto-flow' controls how the auto-placement algorithm works,
specifying exactly how auto-placed items get flowed into the grid.
See [[#auto-placement-algo]] for details on precisely how the auto-placement algorithm works.
row
The auto-placement algorithm places items
by filling each row in turn,
adding new rows as necessary.
If neither ''row'' nor ''column'' is provided,
''row'' is assumed.
column
The auto-placement algorithm places items
by filling each column in turn,
adding new columns as necessary.
dense
If specified, the auto-placement algorithm uses a “dense” packing algorithm,
which attempts to fill in holes earlier in the grid if smaller items come up later.
This may cause items to appear out-of-order,
when doing so would fill in holes left by larger items.
If omitted, a “sparse” algorithm is used,
where the placement algorithm only ever moves “forward” in the grid when placing items,
never backtracking to fill holes.
This ensures that all of the auto-placed items appear “in order”,
even if this leaves holes that could have been filled by later items.
Note: A future level of this module is expected to add a value that flows auto-positioned items together into a single “default” cell.
Auto-placement takes grid items in order-modified document order.
In the following example, there are three columns, each auto-sized to their contents.
No rows are explicitly defined.
The 'grid-auto-flow' property is ''grid-auto-flow/row''
which instructs the grid to search across its three columns starting with the first row,
then the next,
adding rows as needed until sufficient space is located to accommodate the position of any auto-placed grid item.
A form arranged using automatic placement.
<style type="text/css">
form {
display: grid;
/* Define three columns, all content-sized,
and name the corresponding lines. */
grid-template-columns: [labels] auto [controls] auto [oversized] auto;
grid-auto-flow: row dense;
}
form > label {
/* Place all labels in the "labels" column and
automatically find the next available row. */
grid-column: labels;
grid-row: auto;
}
form > input, form > select {
/* Place all controls in the "controls" column and
automatically find the next available row. */
grid-column: controls;
grid-row: auto;
}
#department-block {
/* Auto place this item in the "oversized" column
in the first row where an area that spans three rows
won't overlap other explicitly placed items or areas
or any items automatically placed prior to this area. */
grid-column: oversized;
grid-row: span 3;
}
/* Place all the buttons of the form
in the explicitly defined grid area. */
#buttons {
grid-row: auto;
/* Ensure the button area spans the entire grid element
in the inline axis. */
grid-column: 1 / -1;
text-align: end;
}
</style>
<form>
<label for="firstname">First name:</label>
<input type="text" id="firstname" name="firstname" />
<label for="lastname">Last name:</label>
<input type="text" id="lastname" name="lastname" />
<label for="address">Address:</label>
<input type="text" id="address" name="address" />
<label for="address2">Address 2:</label>
<input type="text" id="address2" name="address2" />
<label for="city">City:</label>
<input type="text" id="city" name="city" />
<label for="state">State:</label>
<select type="text" id="state" name="state">
<option value="WA">Washington</option>
</select>
<label for="zip">Zip:</label>
<input type="text" id="zip" name="zip" />
<div id="department-block">
<label for="department">Department:</label>
<select id="department" name="department" multiple>
<option value="finance">Finance</option>
<option value="humanresources">Human Resources</option>
<option value="marketing">Marketing</option>
</select>
</div>
<div id="buttons">
<button id="cancel">Cancel</button>
<button id="back">Back</button>
<button id="next">Next</button>
</div>
</form>
The 'grid' property is a shorthand that sets
all of the [=explicit grid properties=]
('grid-template-rows', 'grid-template-columns', and 'grid-template-areas'),
and all the [=implicit grid properties=]
('grid-auto-rows', 'grid-auto-columns', and 'grid-auto-flow'),
in a single declaration.
(It does not reset the gutter properties.)
Its syntax matches 'grid-template',
plus an additional syntax form
for defining auto-flow grids:
Sets up auto-flow,
by setting the tracks in one axis explicitly
(setting either 'grid-template-rows' or 'grid-template-columns' as specified,
and setting the other to ''grid-template-rows/none''),
and specifying how to auto-repeat the tracks in the other axis
(setting either 'grid-auto-rows' or 'grid-auto-columns' as specified,
and setting the other to ''grid-auto-rows/auto'').
'grid-auto-flow' is also set to either ''row'' or ''column'' accordingly,
with ''dense'' if it's specified.
All other 'grid' sub-properties are reset to their initial values.
Note: Note that you can only specify the explicit or the implicit grid properties in a single 'grid' declaration.
The sub-properties you don't specify are set to their initial value,
as normal for shorthands.
In addition to accepting the 'grid-template' shorthand syntax for setting up the explicit grid,
the 'grid' shorthand can also easily set up parameters for an auto-formatted grid.
For example, ''grid: auto-flow 1fr / 100px;'' is equivalent to
Every grid item is associated with a grid area,
a rectangular set of adjacent grid cells that the grid item occupies.
This grid area defines the containing block for the grid item
within which the self-alignment properties ('justify-self' and 'align-self') determine their actual position.
The cells that a grid item occupies also influence the sizing of the grid's rows and columns,
defined in [[#layout-algorithm]].
The location of a grid item’sgrid area within the grid
is defined by its placement,
which consists of a grid position and a grid span:
How many grid tracks the grid item occupies in each axis.
In Level 1,
a grid item’s grid span is always definite,
defaulting to 1 in each axis if it can't be otherwise determined for that axis.
The grid-placement properties--
the longhands 'grid-row-start', 'grid-row-end', 'grid-column-start', 'grid-column-end', and their shorthands 'grid-row', 'grid-column', and 'grid-area'--
allow the author to specify a grid item’s placement
by providing any (or none) of the following six pieces of information:
Row
Column
|Start|
row-start line
column-start line
|End|
row-end line
column-end line
|Span|
row span
column span
A definite value for any two of Start, End, and Span in a given dimension implies a definite value for the third.
The following table summarizes the conditions under which a grid position or span is definite or automatic:
Position
Span
Definite
At least one specified line
Explicit, implicit, or defaulted span.
Automatic
No lines explicitly specified
N/A
Common Patterns for Grid Placement
This section is informative.
The grid-placement property longhands are organized into three shorthands:
'grid-area'
'grid-column'
'grid-row'
'grid-column-start'
'grid-column-end'
'grid-row-start'
'grid-row-end'
Named Areas
An item can be placed into a named grid area
(such as those produced by the template in 'grid-template-areas')
by specifying the area’s name in 'grid-area':
article {
grid-area: main;
/* Places item into the named area "main". */
}
An item can also be partially aligned with a named grid area,
with other edges aligned to some other line:
.one {
grid-row-start: main;
/* Align the row-start edge to the start edge of the "main" named area. */
}
Numeric Indexes and Spans
Grid items can be positioned and sized by number,
which is particularly helpful for script-driven layouts:
.two {
grid-row: 2; /* Place item in the second row. */
grid-column: 3; /* Place item in the third column. */
/* Equivalent to grid-area: 2 / 3; */
}
By default, a grid item has a span of 1.
Different spans can be given explicitly:
.three {
grid-row: 2 / span 5;
/* Starts in the 2nd row,
spans 5 rows down (ending in the 7th row). */
}
.four {
grid-row: span 5 / 7;
/* Ends in the 7th row,
spans 5 rows up (starting in the 2nd row). */
}
Note: Note that grid indexes are writing mode relative.
For example, in a right-to-left language like Arabic,
the first column is the rightmost column.
Named Lines and Spans
Instead of counting lines by number,
named lines can be referenced by their name:
.five {
grid-column: first / middle;
/* Span from line "first" to line "middle". */
}
Note: Note that if a named grid area and a named line have the same name,
the placement algorithm will prefer to use named grid area’s lines instead.
If there are multiple lines of the same name,
they effectively establish a named set of grid lines,
which can be exclusively indexed by filtering the placement by name:
.six {
grid-row: text 5 / text 7;
/* Span between the 5th and 7th lines named "text". */
grid-row: text 5 / span text 2;
/* Same as above - start at the 5th line named "text",
then span across two more "text" lines, to the 7th. */
}
Auto Placement
A grid item can be automatically placed into the next available empty grid cell,
growing the grid if there's no space left.
.eight {
grid-area: auto; /* Initial value */
}
This can be used, for example, to list a number of sale items on a catalog site
in a grid pattern.
Auto-placement can be combined with an explicit span,
if the item should take up more than one cell:
.nine {
grid-area: span 2 / span 3;
/* Auto-placed item, covering two rows and three columns. */
}
Whether the auto-placement algorithm searches across and adds rows,
or searches across and adds columns,
is controlled by the 'grid-auto-flow' property.
Note: By default, the auto-placement algorithm looks linearly through the grid without backtracking;
if it has to skip some empty spaces to place a larger item,
it will not return to fill those spaces.
To change this behavior,
specify the ''dense'' keyword in 'grid-auto-flow'.
Grid Item Placement vs. Source Order
“With great power comes great responsibility.”
The abilities of the grid-placement properties
allow content to be freely arranged and reordered within the grid,
such that the visual presentation can be largely disjoint
from the underlying document source order.
These abilities allow the author great freedom
in tailoring the rendering to different devices
and modes of presentation
e.g. using media queries.
However they are not a substitute for correct source ordering.
Correct source order is important for speech,
for sequential navigation (such as keyboard navigation),
and non-CSS UAs such as search engines, tactile browsers, etc.
Grid placement only affects the visual presentation!
This allows authors to optimize the document source for
non-CSS/non-visual interaction modes,
and use grid placement techniques to further manipulate the visual presentation
so as to leave that source order intact.
Line-based Placement: the 'grid-row-start', 'grid-column-start', 'grid-row-end', and 'grid-column-end' properties
Name: grid-row-start, grid-column-start, grid-row-end, grid-column-end
Value: <>
Initial: auto
Applies to: grid items and absolutely-positioned boxes whose containing block is a grid container
Inherited: no
Percentages: n/a
Computed value: specified keyword, identifier, and/or integer
Animation type: discrete
The 'grid-row-start', 'grid-column-start', 'grid-row-end', and 'grid-column-end' properties
determine a grid item’s size and location within the grid
by contributing a line, a span, or nothing (automatic)
to its grid placement,
thereby specifying the inline-start, block-start, inline-end, and block-end edges of its grid area.
Values have the following meanings:
<>
First attempt to match the grid area’s edge to a named grid area:
if there is a named line with the name <>-start (for 'grid-*-start') / <>-end (for 'grid-*-end'),
contributes the first such line to the grid item’s placement.
Note: Named grid areas automatically generate [=implicitly-assigned line names=] of this form,
so specifying ''grid-row-start: foo'' will choose the start edge of that named grid area
(unless another line named ''foo-start'' was explicitly specified before it).
Otherwise,
treat this as if the integer ''1'' had been specified along with the <>.
<> && <>?
Contributes the Nth grid line to the grid item’s placement.
If a negative integer is given,
it instead counts in reverse,
starting from the end edge of the explicit grid.
If a name is given as a <>,
only lines with that name are counted.
If not enough lines with that name exist,
all implicit grid lines
are assumed to have that name for the purpose of finding this position.
An <> value of zero makes the declaration invalid.
span && [ <> || <> ]
Contributes a grid span to the grid item’s placement
such that the corresponding edge of the grid item’s grid area is N lines from its opposite edge
in the corresponding direction.
For example, ''grid-column-end: span 2'' indicates the second grid line in the endward direction
from the 'grid-column-start' line.
If a name is given as a <>,
only lines with that name are counted.
If not enough lines with that name exist,
all implicit grid lines
on the side of the explicit grid corresponding to the search direction
are assumed to have that name for the purpose of counting this span.
The grid container has an explicit grid with two grid lines,
numbered 1 and 2.
The grid item's column-end edge is specified to be at line 4,
so two lines are generated in the endward side of the implicit grid.
Its column-start edge must be the first "foo" line it can find startward of that.
There is no "foo" line in the grid, though,
so the only possibility is a line in the implicit grid.
Line 3 is not a candidate, because it's on the endward side of the explicit grid,
while the 'grid-column-start' span forces it to search startward.
So, the only option is for the implicit grid to generate a line on the startward side of the explicit grid.
An illustration of the result.
If the <> is omitted, it defaults to ''1''.
Negative integers or zero are invalid.
auto
The property contributes nothing to the grid item’s placement,
indicating auto-placement or a default span of one.
(See [[#placement]], above.)
In all the above productions,
the <> additionally excludes the keywords span and auto.
Given a single-row, 8-column grid and the following 9 named lines:
1 2 3 4 5 6 7 8 9
+--+--+--+--+--+--+--+--+
| | | | | | | | |
A B C A B C A B C
| | | | | | | | |
+--+--+--+--+--+--+--+--+
The following declarations place the grid item between the lines indicated by index:
grid-column-start: 4; grid-column-end: auto;
/* Line 4 to line 5 */
grid-column-start: auto; grid-column-end: 6;
/* Line 5 to line 6 */
grid-column-start: C; grid-column-end: C -1;
/* Line 3 to line 9 */
grid-column-start: C; grid-column-end: span C;
/* Line 3 to line 6 */
grid-column-start: span C; grid-column-end: C -1;
/* Line 6 to line 9 */
grid-column-start: span C; grid-column-end: span C;
/* Error: The end span is ignored, and an auto-placed
item can't span to a named line.
Equivalent to ''grid-column: span 1;''. */
grid-column-start: 5; grid-column-end: C -1;
/* Line 5 to line 9 */
grid-column-start: 5; grid-column-end: span C;
/* Line 5 to line 6 */
grid-column-start: 8; grid-column-end: 8;
/* Error: line 8 to line 9 */
grid-column-start: B 2; grid-column-end: span 1;
/* Line 5 to line 6 */
Grid Placement Conflict Handling
If the placement for a grid item contains two lines,
and the start line is further end-ward than the end line,
swap the two lines.
If the start line is equal to the end line,
remove the end line.
If the placement contains two spans,
remove the one contributed by the endgrid-placement property.
If the placement contains only a span for a named line,
replace it with a span of 1.
Placement Shorthands: the 'grid-column', 'grid-row', and 'grid-area' properties
Name: grid-row, grid-column
Value: <> [ / <> ]?
Initial: auto
Applies to: grid items and absolutely-positioned boxes whose containing block is a grid container
Inherited: no
Percentages: N/A
Animation type: discrete
The 'grid-row' and 'grid-column' properties are shorthands for 'grid-row-start'/'grid-row-end' and 'grid-column-start'/'grid-column-end', respectively.
If two <> values are specified,
the 'grid-row-start'/'grid-column-start' longhand is set to the value before the slash,
and the 'grid-row-end'/'grid-column-end' longhand is set to the value after the slash.
When the second value is omitted,
if the first value is a <>,
the 'grid-row-end'/'grid-column-end' longhand is also set to that <>;
otherwise, it is set to auto.
Name: grid-area
Value: <> [ / <> ]{0,3}
Initial: auto
Applies to: grid items and absolutely-positioned boxes whose containing block is a grid container
Inherited: no
Percentages: N/A
Animation type: discrete
The 'grid-area' property is a shorthand for
'grid-row-start', 'grid-column-start', 'grid-row-end' and 'grid-column-end'.
If four <> values are specified,
'grid-row-start' is set to the first value,
'grid-column-start' is set to the second value,
'grid-row-end' is set to the third value,
and 'grid-column-end' is set to the fourth value.
When 'grid-column-end' is omitted,
if 'grid-column-start' is a <>,
'grid-column-end' is set to that <>;
otherwise, it is set to auto.
When 'grid-row-end' is omitted,
if 'grid-row-start' is a <>,
'grid-row-end' is set to that <>;
otherwise, it is set to auto.
When 'grid-column-start' is omitted,
if 'grid-row-start' is a <>,
all four longhands are set to that value.
Otherwise, it is set to auto.
Note: The resolution order for this shorthand is row-start/column-start/row-end/column-end,
which goes CCW for LTR pages,
the opposite direction of the related 4-edge properties using physical directions, like 'margin'.
Grid Item Placement Algorithm
The following grid item placement algorithm
resolves automatic positions of grid items into definite positions,
ensuring that every grid item has a well-defined grid area to lay out into.
(Grid spans need no special resolution;
if they're not explicitly specified,
they default to 1.)
Note: This algorithm can result in the creation of new rows or columns in the implicit grid,
if there is no room in the explicit grid to place an auto-positioned grid item.
Every grid cell
(in both the explicit and implicit grids)
can be occupied or unoccupied.
A cell is occupied
if it's covered by the grid area
of a grid item with a definite grid position;
otherwise,
the cell is unoccupied.
A cell's occupied/unoccupied status can change during this algorithm.
To aid in clarity,
this algorithm is written with the assumption that 'grid-auto-flow'
has ''grid-auto-flow/row'' specified.
If it is instead set to ''grid-auto-flow/column'',
swap all mentions of rows and columns, inline and block, etc. in this algorithm.
Note: The auto-placement algorithm works with the grid items in order-modified document order,
not their original document order.
0. Generate anonymous grid items
as described in [[#grid-items]].
(Anonymous grid items are always auto-placed,
since their boxes can't have any grid-placement properties specified.)
1. Position anything that's not auto-positioned.
2. Process the items locked to a given row.
For each grid item with a definite row position
(that is, the 'grid-row-start' and 'grid-row-end' properties define a definite grid position),
in order-modified document order:
: “sparse” packing (default behavior)
::
Set the column-start line of its placement
to the earliest (smallest positive index) line index
that ensures this item’s grid area will not overlap any occupied grid cells
and that is past any grid items previously placed in this row by this step.
: “dense” packing (''dense'' specified)
::
Set the column-start line of its placement
to the earliest (smallest positive index) line index
that ensures this item’s grid area will not overlap any occupied grid cells.
3. Determine the columns in the implicit grid.
Create columns in the implicit grid:
1. Start with the columns from the explicit grid.
2. Among all the items with a definite column position
(explicitly positioned items, items positioned in the previous step, and items not yet positioned but with a definite column)
add columns to the beginning and end of the implicit grid
as necessary to accommodate those items.
3. If the largest column span among all the items without a definite column position
is larger than the width of the implicit grid,
add columns to the end of the implicit grid to accommodate that column span.
The number of columns needed is 6.
The explicit grid provides 5 columns
(from 'grid-template-columns')
with lines number 1 through 6,
but #grid-item’s column position means it ends on line 7,
which requires an additional column added to the end of the implicit grid.
4. Position the remaining grid items.
The auto-placement cursor defines the current “insertion point” in the grid,
specified as a pair of row and column grid lines.
Initially the auto-placement cursor is set to the start-most row and column lines in the implicit grid.
The 'grid-auto-flow' value in use determines how to position the items:
: “sparse” packing (default behavior)
:: For each grid item that hasn't been positioned by the previous steps,
in order-modified document order:
: If the item has a definite column position:
::
1. Set the column position of the cursor to the grid item’s column-start line.
If this is less than the previous column position of the cursor,
increment the row position by 1.
2. Increment the cursor’s row position until a value is found
where the grid item does not overlap any occupied grid cells
(creating new rows in the implicit grid as necessary).
3. Set the item's row-start line to the cursor's row position,
and set the item's row-end line according to its span from that position.
: If the item has an automatic grid position in both axes:
::
1. Increment the column position of the auto-placement cursor
until either this item’s grid area does not overlap any occupied grid cells,
or the cursor's column position,
plus the item's column span,
overflow the number of columns in the implicit grid,
as determined earlier in this algorithm.
2. If a non-overlapping position was found in the previous step,
set the item's row-start and column-start lines to the cursor's position.
Otherwise,
increment the auto-placement cursor’s row position
(creating new rows in the implicit grid as necessary),
set its column position to the start-most column line in the implicit grid,
and return to the previous step.
: “dense” packing (''dense'' specified)
:: For each grid item that hasn't been positioned by the previous steps,
in order-modified document order:
: If the item has a definite column position:
::
1. Set the row position of the cursor to the start-most row line in the implicit grid.
Set the column position of the cursor to the grid item’s column-start line.
2. Increment the auto-placement cursor’s row position until a value is found
where the grid item does not overlap any occupied grid cells
(creating new rows in the implicit grid as necessary).
3. Set the item's row-start line index to the cursor's row position.
(Implicitly setting the item's row-end line according to its span, as well.)
: If the item has an automatic grid position in both axes:
::
1. Set the cursor's row and column positions to start-most row and column lines in the implicit grid.
2. Increment the column position of the auto-placement cursor
until either this item’s grid area does not overlap any occupied grid cells,
or the cursor's column position,
plus the item's column span,
overflow the number of columns in the implicit grid,
as determined earlier in this algorithm.
3. If a non-overlapping position was found in the previous step,
set the item's row-start and column-start lines to the cursor's position.
Otherwise,
increment the auto-placement cursor’s row position
(creating new rows in the implicit grid as necessary),
reset its column position to the start-most column line in the implicit grid,
and return to the previous step.
Absolute Positioning
With a Grid Container as Containing Block
If an absolutely positioned element's containing block
is generated by a grid container,
the containing block corresponds to the grid area determined by its grid-placement properties.
The offset properties ('top'/'right'/'bottom'/'left')
then indicate offsets inwards from the corresponding edges
of this containing block, as normal.
Note: While absolutely-positioning an element to a grid container
does allow it to align to that container's grid lines,
such elements do not take up space or otherwise participate in the layout of the grid.
.grid {
grid: 1fr 1fr 1fr 1fr / 10rem 10rem 10rem 10rem;
/* 4 equal-height rows filling the grid container,
4 columns of ''10rem'' each */
justify-content: center;
/* center the grid horizontally within the grid container */
position: relative;
/* Establish abspos containing block */
}
.abspos {
grid-row-start: 1; /* 1st grid row line = top of grid container */
grid-row-end: span 2; /* 3rd grid row line */
grid-column-start: 3; /* 3rd grid col line */
grid-column-end: auto; /* right padding edge */
/* Containing block covers the top right quadrant of the grid container */
position: absolute;
top: 70px;
bottom: 40px;
left: 100px;
right: 30px;
}
Note: Grids and the grid-placement properties are flow-relative,
while the offset properties ('left', 'right', 'top', and 'bottom') are physical,
so if the 'direction' or 'writing-mode' properties change,
the grid will transform to match,
but the offsets won't.
Instead of auto-placement, an ''auto'' value for a grid-placement property
contributes a special line to the placement
whose position is that of the corresponding padding edge of the grid container
(the padding edge of the scrollable area, if the grid container overflows).
These lines become the first and last lines (0th and -0th) of the augmented grid
used for positioning absolutely-positioned items.
Note: Thus, by default, the absolutely-positioned box's containing block will correspond
to the padding edges of the grid container, as it does for block containers.
Absolute positioning occurs after layout of the grid and its in-flow contents,
and does not contribute to the sizing of any grid tracks
or affect the size/configuration of the grid in any way.
If a grid-placement property refers to a non-existent line
either by explicitly specifying such a line or by spanning outside of the existing implicit grid,
it is instead treated as specifying ''auto''
(instead of creating new implicit grid lines).
Note: Remember that implicit lines are assumed to have all line names,
so a referenced line might exist even though it is not explicitly named.
If the placement only contains a grid span,
replace it with the two ''auto'' lines in that axis.
(This happens when both grid-placement properties in an axis contributed a span originally,
and [[#grid-placement-errors]] caused the second span to be ignored.)
With a Grid Container as Parent
An absolutely-positioned child of a grid container
is out-of-flow and not a grid item,
and so does not affect the placement of other items
or the sizing of the grid.
The static position [[!CSS2]]
of an absolutely-positioned child of a grid container
is determined as if it were the sole grid item
in a grid area
whose edges coincide with the content edges of the grid container.
However, if the grid container parent is also the generator of the absolutely positioned element's containing block,
instead use the grid area determined in [[#abspos-items]].
Note: Note that this position is affected by the values of 'justify-self' and 'align-self' on the child,
and that, as in most other layout models,
the absolutely-positioned child has no effect on the size of the containing block
or layout of its contents.
Alignment and Spacing
After a grid container’s grid tracks have been sized,
and the dimensions of all grid items are finalized,
grid items can be aligned within their grid areas.
The 'margin' properties can be used to align items in a manner similar to
what margins can do in block layout.
Grid items also respect the box alignment properties
from the CSS Box Alignment Module [[!CSS-ALIGN-3]],
which allow easy keyword-based alignment of items in both the rows and columns.
By default,
grid items stretch to fill their grid area.
However, if 'justify-self' or 'align-self' compute to a value other than ''justify-self/stretch''
or margins are auto,
grid items will auto-size to fit their contents.
Gutters: the 'row-gap', 'column-gap', and 'gap' properties
The 'row-gap' and 'column-gap' properties
(and their 'gap' shorthand),
when specified on a grid container,
define the [=gutters=] between grid rows and grid columns.
Their syntax is defined in [[css-align-3#gaps]].
The effect of these properties
is as though the affected grid lines acquired thickness:
the grid track between two grid lines
is the space between the gutters that represent them.
For the purpose of [[#algo-track-sizing|track sizing]],
each gutter is treated as
an extra, empty, fixed-size track of the specified size,
which is spanned by any grid items
that span across its corresponding grid line.
Note: Additional spacing may be added between tracks
due to 'justify-content'/'align-content'.
See [[#algo-overview]].
This space effectively increases the size of the gutters.
If a grid is fragmented between tracks,
the gutter spacing between those tracks must be suppressed.
Note that gutters are suppressed even after forced breaks,
unlike margins.Gutters only appear between tracks of the implicit grid;
there is no gutter before the first track or after the last track.
(In particular, there is no gutter between the first/last track of the implicit grid
and the “auto” lines in the augmented grid.)
When a collapsed track’s gutters collapse,
they coincide exactly--
the two gutters overlap so that their start and end edges coincide.
If one side of a collapsed track does not have a gutter
(e.g. if it is the first or last track of the implicit grid),
then collapsing its gutters results in no gutter
on either “side” of the collapsed track.
This section is non-normative.
The normative definition of how margins affect grid items is in [[#layout-algorithm]].
Auto margins on grid items have an effect very similar to auto margins in block flow:
During calculations of grid track sizes, auto margins are treated as ''0''.
''margin/auto'' margins absorb positive free space
prior to alignment via the box alignment properties.
Overflowing elements ignore their ''margin/auto'' margins
and overflow as specified by their box alignment properties.
Inline-axis Alignment: the 'justify-self' and 'justify-items' properties
Grid items can be aligned in the inline dimension
by using the 'justify-self' property on the grid item
or 'justify-items' property on the grid container,
as defined in [[!CSS-ALIGN-3]].
For example,
for an English document,
the inline axis is horizontal,
and so the 'justify-*' properties align the grid items horizontally.
If baseline alignment is specified on a grid item
whose size in that axis depends on the size of an intrinsically-sized track
(whose size is therefore dependent on both the item's size and baseline alignment,
creating a cyclic dependency),
that item does not participate in baseline alignment,
and instead uses its fallback alignment
as if that were originally specified.
For this purpose, <> track sizes count as “intrinsically-sized”
when the [=grid container=] has an [=indefinite=] size in the relevant axis.
Note: Whether the fallback alignment is used or not
does not change over the course of layout:
if a cycle exists, it exists.
Block-axis Alignment: the 'align-self' and 'align-items' properties
Grid items can also be aligned in the block dimension
(perpendicular to the inline dimension)
by using the 'align-self' property on the grid item
or 'align-items' property on the grid container,
as defined in [[!CSS-ALIGN-3]].
If baseline alignment is specified on a grid item
whose size in that axis depends on the size of an intrinsically-sized track
(whose size is therefore dependent on both the item's size and baseline alignment,
creating a cyclic dependency),
that item does not participate in baseline alignment,
and instead uses its fallback alignment
as if that were originally specified.
For this purpose, <> track sizes count as “intrinsically-sized”
when the [=grid container=] has an [=indefinite=] size in the relevant axis.
Aligning the Grid: the 'justify-content' and 'align-content' properties
If the grid’s outer edges do not correspond to the grid container’s content edges
(for example, if no columns are flex-sized),
the grid tracks are aligned within the content box according to the 'justify-content' and 'align-content' properties on the grid container.
For example, the following grid is centered vertically,
and aligned to the right edge of its grid container:
If there are no grid tracks
(the explicit grid is empty, and no tracks were created in the implicit grid),
the sole grid line in each axis is aligned with the start edge of the grid container.
Note that certain values of 'justify-content' and 'align-content'
can cause the tracks to be spaced apart
(''justify-content/space-around'', ''justify-content/space-between'', ''justify-content/space-evenly'')
or to be resized (''<content-distribution>/stretch'').
If the grid is fragmented between tracks,
any such additional spacing between those tracks must be suppressed.
For example, in the following grid,
the spanning item’s grid area is increased to accommodate
the extra space assigned to the gutters due to alignment:
Grid before alignmentGrid after alignment
Note that alignment (unlike 'gap' spacing)
happens after the grid tracks are sized,
so if the track sizes are determined by the contents of the spanned item,
it will gain excess space in the alignment stage
to accommodate the alignment spacing.
Grid Container Baselines
The first (last) baselines of a grid container
are determined as follows:
Find the first (last) row of the [=grid container=]
containing at least one [=grid item=].
If any of the [=grid items=] intersecting this row
participate in [=baseline alignment=] in that row,
the grid container's baseline set
is generated from
the shared alignment baseline of those grid items.
Otherwise,
the grid container's first (last) baseline set
is generated from
the alignment baseline of the first (last) grid item
in row-major grid order (according to the writing mode of the grid container).
If the [=grid item=] has no alignment baseline in the grid's inline axis,
then one is first synthesized
from its border edges.
If the [=grid container=] does not contain any [=grid items=],
the grid container has no first (last) baseline set,
and one is synthesized if needed
according to the rules of its alignment context.
Exit from this algorithm.
Grid-modified document order (grid order)
is the order in which grid items are encountered
when traversing the grid's grid cells.
If two items are encountered at the same time,
they are taken in order-modified document order.
When calculating the baseline according to the above rules,
if the box contributing a baseline has an 'overflow' value that allows scrolling,
the box must be treated as being in its initial scroll position
for the purpose of determining its baseline.
When determining the baseline of a table cell,
a grid container provides a baseline just as a line box or table-row does. [[!CSS2]]
See [[css-writing-modes-3#intro-baselines]]
and [[css-align-3#baseline-rules]]
for more information on baselines.
Grid Sizing
This section defines the grid sizing algorithm,
which determines the size of all grid tracks
and, by extension, the entire grid.
Each track has specified minimum and
maximumsizing functions
(which may be the same).
Each sizing function is either:
A fixed sizing function (<> or resolvable <>).
An intrinsic sizing function (''min-content'', ''max-content'', ''auto'', ''fit-content()'').
A flexible sizing function (<>).
The grid sizing algorithm defines how to resolve these sizing constraints into used track sizes.
Grid Sizing Algorithm
First, the track sizing algorithm is used to resolve the sizes of the grid columns.
If calculating the layout of a grid item in this step
depends on the available space in the block axis,
assume the available space that it would have
if any row with a definitemax track sizing function
had that size and all other rows were infinite.
If both the grid container and all tracks have definite sizes,
also apply 'align-content' to find the final effective size
of any gaps spanned by such items;
otherwise ignore the effects of track alignment in this estimation.
Would it help to have heuristics
that attempt a more accurate initial estimate?
E.g. assuming the available space that it would have as the maximum of:
the sum of all definite track sizes that it spans
(using the maximum of a track’s min and max sizing functions,
if both are definite,
the argument to ''fit-content()'' if that is definite).
the item’s ''min-content'' size,
if any track that it spans
has a ''min-content'' or ''fit-content()'' sizing function.
the item's automatic minimum size,
if any track that it spans
has an ''auto'' min sizing function.
infinity, if any track that it spans
has a ''max-content'' min sizing function
or a ''max-content'', ''auto'', or <> max sizing function.
This is may reduce the amount of re-layout passes that are necessary,
but will it produce a different or better result in any cases?
Should we adopt it into the spec?
Finally, the grid container is sized
using the resulting size of the grid as its content size,
and the tracks are aligned within the grid container
according to the 'align-content' and 'justify-content' properties.
Note: This can introduce extra space between tracks,
potentially enlarging the grid area of any grid items spanning the gaps
beyond the space allotted to during track sizing.
Once the size of each grid area is thus established,
the grid items are laid out into their respective containing blocks.
The grid area’s width and height are considered definite for this purpose.
Note: Since formulas calculated using only definite sizes,
such as the stretch fit formula,
are also definite,
the size of a grid item which is stretched
is also considered definite.
Track Sizing Terminology
min track sizing function
If the track was sized with a ''minmax()'' function,
this is the first argument to that function.
If the track was sized with a <> value or ''fit-content()'' function,
''auto''.
Otherwise, the track's sizing function.
max track sizing function
If the track was sized with a ''minmax()'' function,
this is the second argument to that function.
Otherwise, the track's sizing function.
In all cases, treat ''auto'' and ''fit-content()'' as ''max-content'',
except where specified otherwise for ''fit-content()''.
available grid space
Independently in each dimension, the available grid space is:
* If the grid container's size is definite,
then use the size of its content box.
* If the grid container is being sized under
a min-content constraint or max-content constraint
then the available grid space is that constraint
(and is indefinite).
Note: ''auto'' sizes that indicate content-based sizing (e.g. the height of a block-level box in horizontal writing modes) are equivalent to ''max-content''.
In all cases, clamp the available grid space
according to the grid container's min/max-width/height properties,
if they are definite.
Note: Remember that [[#gutters|gutters]] are treated as fixed-size tracks--
tracks with their min and max sizing functions both set to the gutter’s used size--
for the purpose of the grid sizing algorithm.
Their widths need to be incorporated into
the track sizing algorithm’s calculations accordingly.
Track Sizing Algorithm
The remainder of this section is the track sizing algorithm,
which calculates from the min and max track sizing functions
the used track size.
Each track has a base size,
a <> which grows throughout the algorithm
and which will eventually be the track's final size,
and a growth limit,
a <> which provides a desired maximum size for the base size.
There are 5 steps:
[[#algo-init|Initialize Track Sizes]]
[[#algo-content|Resolve Intrinsic Track Sizes]]
[[#algo-grow-tracks|Maximize Tracks]]
[[#algo-flex-tracks|Expand Flexible Tracks]]
[[#algo-stretch|Expand Stretched auto Tracks]]
Initialize Track Sizes
Initialize each track's base size and growth limit.
For each track,
if the track's min track sizing function is:
Resolve to an absolute length and use that size as the track’s initial base size.
Note: Indefinite lengths cannot occur,
as they're treated as ''auto''.
This step resolves intrinsic track sizing functions to absolute lengths.
First it resolves those sizes based on items that are contained wholly within a single track.
Then it gradually adds in the space requirements of items that span multiple tracks,
evenly distributing the extra space across those tracks
insofar as possible.
Note: When this step is complete,
all intrinsic base sizes and growth limits
will have been resolved to absolute lengths.
Note: [[#algo-terms|Remember that]] ''fit-content()'' and ''auto'' [=max track sizing functions=]
are treated the same as ''max-content''
except where explicitly specified otherwise.
Shim baseline-aligned items
so their intrinsic size contributions reflect their baseline alignment.
For the items in each baseline-sharing group,
add a “shim” (effectively, additional margin)
on the start/end side (for first/last-baseline alignment)
of each item
so that,
when start/end-aligned together
their [[css-align-3#baseline-values|baselines align as specified]].
Consider these “shims” as part of the items’ intrinsic size contribution
for the purpose of track sizing, below.
If an item uses multiple intrinsic size contributions,
it can have different shims for each one.
For example, when the grid container has an indefinite size,
it is first laid out under min/max-content constraints to find the size,
then laid out "for real" with that size
(which can affect things like percentage tracks).
The "shims" added for each phase are independent,
and only affect the layout during that phase.
Note: Note that both [[css-align-3#baseline-align-self|baseline self-aligned]]
and [[css-align-3#baseline-align-content|baseline content-aligned]] items
are considered in this step.
Note: Since grid items whose own size
depends on the size of an intrinsically-sized track
[[#row-align|do not participate in baseline alignment]],
they are not shimmed.
In all cases, if a track’s growth limit is now less than its base size,
increase the growth limit to match the base size.
Note: This step is a simplification of the steps below for handling spanning items,
and should yield the same behavior as running those instructions
on items with a span of 1.
Increase sizes to accommodate spanning items crossing content-sized tracks:
Next, consider the items with a span of 2
that do not span a track with a flexible sizing function.
For content-based minimums:
Next continue to increase the base size of tracks with
a min track sizing function of ''min-content'' or ''max-content''
by [[#extra-space|distributing extra space]] as needed
to account for these items' min-content contributions.
Consider the following case:
Two "auto" tracks (i.e. ''minmax(min-content, max-content) minmax(min-content, max-content)'').
Item 1 is in track 1, and has min-content = max-content = 10.
Item 2 spans tracks 1 and 2, and has min-content = 30, max-content = 100.
After resolving min-content/max-content for the first item, we have this.
track 1: base size = 10 growth limit = 10
track 2: base size = 0 growth limit = infinity
Then we resolve min-content/max-content for the second item.
Phase 1 sets the base size of track 2 to 20 so that the two tracks' base sizes sum to 30.
Phase 2 does nothing because there are no relevant tracks.
Phase 3 sets the growth limit of track 2 to 20 so that the two tracks' growth limits sum to 30.
In phase 4, we need to grow the sum of the growth limits by 70 to accommodate item 2.
Two options are:
1. Grow each track's growth limit equally,
and end up with growth limits = [45, 55].
2. Grow only the second track's growth limit,
and end up with growth limits = [10, 90].
By not considering the just-set growth limit as a constraint during space distribution
(i.e. by treating it as infinity),
we get the second result,
which we considered a better result because the first track remains sized exactly to the first item.
For max-content maximums:
Lastly continue to increase the growth limit of tracks with
a max track sizing function of ''max-content''
by [[#extra-space|distributing extra space]] as needed
to account for these items' max-content contributions.
However, limit the growth of any ''fit-content()'' tracks
by their ''fit-content()'' argument.
Repeat incrementally for items with greater spans until all items have been considered.
Increase sizes to accommodate spanning items crossing flexible tracks:
Next, repeat the previous step
instead considering (together, rather than grouped by span size)
all items
that do span a track with a flexible sizing function
while
Note: There is no single way to satisfy intrinsic sizing constraints
when items span across multiple tracks.
This algorithm embodies a number of heuristics
which have been seen to deliver good results on real-world use-cases,
such as the “game”̣ examples earlier in this specification.
This algorithm may be updated in the future
to take into account more advanced heuristics as they are identified.
Distributing Extra Space Across Spanned Tracks
To distribute extra space
by increasing the affected sizes of a set of tracks
as required by a set of intrinsic size contributions,
Maintain separately for each affected base size or growth limit
a |planned increase|,
initially set to 0.
(This prevents the size increases from becoming order-dependent.)
For each considered item,
Find the space to distribute:
Subtract the corresponding size (base size or growth limit) of every spanned track
from the item's size contribution to find the item's remaining size contribution.
(For infinite growth limits, substitute the track's base size.)
This is the space to distribute. Floor it at zero.
Distribute space up to limits:
Find the |item-incurred increase| for each spanned track with an affected size
by: distributing the space equally among such tracks,
freezing a track’s |item-incurred increase|
as its affected size + |item-incurred increase|
reaches its |limit|
(and continuing to grow the unfrozen tracks as needed).
For [=base sizes=],
the |limit| is its [=growth limit=].
For [=growth limits=],
the |limit| is infinity if it is marked as [=infinitely growable=],
and equal to the [=growth limit=] otherwise.
Note: If the affected size was a growth limit
and the track is not marked [=infinitely growable=],
then each |item-incurred increase| will be zero.
Distribute space beyond limits:
If space remains after all tracks are frozen,
unfreeze and continue to distribute space to the |item-incurred increase| of…
when handling any intrinsic growth limit:
all affected tracks.
For this purpose,
the [=max track sizing function=] of a ''fit-content()'' track
is treated as ''max-content''
until it reaches the limit specified as the ''fit-content()'' argument,
after which it is treated as having a fixed sizing function of that argument.
Note: This step prioritizes the distribution of space
for accommodating space required
by the tracks’ [=min track sizing functions=]
beyond their current growth limits
based on the types of their [=max track sizing functions=].
For each affected track,
if the track’s |item-incurred increase| is larger than the track’s |planned increase|
set the track’s |planned increase| to that value.
Update the tracks' affected sizes
by adding in the |planned increase|
so that the next round of space distribution will account for the increase.
(If the affected size is an infinite growth limit,
set it to the track's base size plus the |planned increase|.)
For each flexible track,
if the flexible track's flex factor is greater than one,
the result of dividing the track's base size by its flex factor;
otherwise,
the track's base size.
For each [=grid item=] that crosses a flexible track,
the result of
[[#algo-find-fr-size|finding the size of an fr]]
using all the grid tracks that the item crosses
and a space to fill of the item's max-content contribution.
This algorithm finds the largest size that an ''fr'' unit can be
without exceeding the target size.
It must be called with a set of grid tracks
and some quantity of space to fill.
Grid containers can break across pages
between rows or columns
and inside items.
The break-* properties apply to grid containers
as normal for the formatting context in which they participate.
This section defines how they apply to grid items
and the contents of grid items.
The exact layout of a fragmented grid container is not defined in this level of Grid Layout.
However, breaks inside a grid container are subject to the following rules:
The 'break-before' and 'break-after' properties on grid items
are propagated to their grid row.
The 'break-before' property on the first row
and the 'break-after' property on the last row
are propagated to the grid container.
A forced break inside a grid item effectively increases the size of its contents;
it does not trigger a forced break inside sibling items.
Class A break opportunities occur
between rows or columns (whichever is in the appropriate axis),
and Class C break opportunities occur
between the first/last row (column) and the grid container's content edges.
[[!CSS3-BREAK]]
When a grid container is continued after a break,
the space available to its grid items
(in the block flow direction of the fragmentation context)
is reduced by the space consumed by grid container fragments on previous pages.
The space consumed by a grid container fragment is
the size of its content box on that page.
If as a result of this adjustment the available space becomes negative,
it is set to zero.
Aside from the rearrangement of items imposed by the previous point,
UAs should attempt to minimize distortion of the grid container
with respect to unfragmented flow.
Sample Fragmentation Algorithm
This section is non-normative.
This is a rough draft of one possible fragmentation algorithm,
and still needs to be severely cross-checked with the [[CSS-FLEXBOX-1]] algorithm for consistency.
Feedback is welcome; please reference the rules above instead as implementation guidance.
Layout the grid following the [[#layout-algorithm]] by using the
fragmentation container’s inline size and assume unlimited block size.
During this step all 'grid-row' ''auto'' and ''fr'' values must be resolved.
Layout the grid container using the values resolved in the previous step.
If a grid area’s size changes due to fragmentation (do not include items that
span rows in this decision), increase the grid row size as necessary for rows that either:
have a content min track sizing function.
are in a grid that does not have an explicit height and the grid row is flexible.
If the grid height is ''auto'', the height of the grid should be the sum of the final
row sizes.
If a grid area overflows the grid container due to margins being collapsed during
fragmentation, extend the grid container to contain this grid area (this step is
necessary in order to avoid circular layout dependencies due to fragmentation).
If the grid’s height is specified, steps three and four may cause the grid rows to
overflow the grid.
Acknowledgements
This specification is made possible by input from
Erik Anderson,
Rachel Andrew,
Rossen Atanassov,
Oriol Brufau,
Manuel Rego Casasnovas,
Arron Eicholz,
Javier Fernandez,
Sylvain Galineau,
Markus Mielke,
Daniel Holbert,
John Jansen,
Chris Jones,
Kathy Kam,
Veljko Miljanic,
Charbel Nicolas,
Mats Palmgren,
François Remy,
Sergio Villar Senin,
Jen Simmons,
Christian Stockwell,
Eugene Veselov,
and the CSS Working Group members,
with special thanks to
Rossen Atanassov, Alex Mogilevsky, Phil Cupp, and Peter Salas of Microsoft for creating the initial proposal.
Thanks also to Eliot Graff for editorial input.
Changes
This section documents the changes since previous publications.
Removed the option for grid-item block-axis margins and paddings
to be resolved against the block dimension;
they must be resolved against the inline dimension, as for blocks.
(Issue 2085)
grid-items/grid-items-percentage-margins-001.html
Adjusted handling of items spanning flexible tracks
to intrinsic track sizes so that
they contribute to the size of flexible tracks that have an intrinsic min
rather than being ignored.
(Issue 2177)
Increase sizes to accommodate spanning items crossing flexible tracks:
Next, repeat the previous step
instead considering (together, rather than grouped by span size)
all items
that do span a track with a flexible sizing function
while
Limited the contributions of items to an ''grid-template-columns/auto'' minimum track
to not overflow a fixed maximum when sizing the grid under a min-content/max-content constraint.
(Issue 2303)
Better incorporated the alignment of tracks
('align-content'/'justify-content')
into the track sizing algorithm.
(Issue 2557,
Issue 2697)
layout-algorithm/grid-content-distribution-must-account-for-track-sizing-001.html
layout-algorithm/grid-content-distribution-must-account-for-track-sizing-002.html
layout-algorithm/grid-content-distribution-must-account-for-track-sizing-003.html
layout-algorithm/grid-content-distribution-must-account-for-track-sizing-004.html
Require the used value of a track listing
to be serialized without using ''repeat()'' notation.
(Issue 2427)
parsing/grid-template-columns-computed.html
parsing/grid-template-columns-computed-withcontent.html
Specify a minimum number of tracks that a UA should support
(absent memory pressure or similar).
(Issue 2261)
Since memory is limited,
UAs may clamp the possible size of the grid
to be within a UA-defined limit
(which should accommodate lines at in the range [-10000, 10000]),,
dropping all lines outside that limit.
If a grid item is placed outside this limit,
its grid area must be clamped to within this limited grid.
grid-definition/grid-limits-001.html
Exclude 'auto' from line name <>.
(Issue 2856)
parsing/grid-area-invalid.html
parsing/grid-template-columns-invalid.html
parsing/grid-template-rows-invalid.html
The static position of a grid container child
should be resolved against the content edge, not padding edge, of the grid container.
(Issue 3020)
The static position [[!CSS2]]
of an absolutely-positioned child of a grid container
is determined as if it were the sole grid item
in a grid area
whose edges coincide with the padding content edges of the grid container.
The grid (and surrounding padding) is included in the scrollable overflow area.
See [[#overflow]].
(Issue 3638,
Issue 3665)
grid-model/grid-overflow-padding-001.html
grid-model/grid-overflow-padding-002.html
Don't calculate growth limits of flexible tracks as intrinsic sizes;
set them to the base size at the end of intrinsic track sizing
so that they don't grow during Maximize Tracks
(due to differences between interpreting ''grid-template-columns/auto''
min track sizing functions and max track sizing functions, etc.).
(Issue 3693)
Revert unintentional change to ignore items past the first row
for the purpose of finding the grid container’s baselines.
Also clarify the traversal order.
(Issue 3645)
Floor the max track sizing function by the min track sizing function
when calculating the number of ''auto-fit'' or ''auto-fill'' repetitions.
(Issue 4043)
This change is purely editorial; it should have no effect on implementations.
Clarified that white space is normalized in 'grid-template-areas' <>values.
(Issue 4335)
See [[#serialize-template]].
grid-definition/grid-support-grid-template-areas-001.html
Properly specified that the "use baseline-aligned items if possible"
and "use first item that shows up, even if not in the first row"
conditions properly combine together,
so if there's nothing in the first row
but a baseline-aligned item in the second,
we'll use that
(rather than just taking the first item in that row).
Part of Issue 3645.
Find the first (last) row of the [=grid container=]
containing at least one [=grid item=].
Otherwise, the grid container has no first (last) baseline set,
If the [=grid container=] does not contain any [=grid items=],
the grid container has no first (last) baseline set,
and one is synthesized if needed
according to the rules of its alignment context.
alignment/grid-baseline-004.html
Properly limit the item search to just
the items participating in the correct baseline alignment.
(Issue 5293)
If any of the [=grid items=] intersecting this row
participate in [=baseline alignment=] in that row,
the grid container's baseline set
is generated from
the shared alignment baseline of those grid items.
alignment/grid-baseline-004.html
Required 'grid-template-areas' to define at least one cell in the grid;
''grid-template-areas: "" "";'' is invalid.
(Issue 5110)
All strings must have the same number of columns
cell tokens
([=named cell tokens=] and/or [=null cell tokens=]),
and at least one cell token,
or else the declaration is invalid.
parsing/grid-template-areas-one-cell.html
Revert accidental change of [=min-content contribution=] to [=minimum contribution=]
in distributing space for intrinsic [=max track sizing functions=].
(Issue 4790)
For intrinsic maximums:
Next increase the growth limit of tracks with
an intrinsicmax track sizing function
by [[#extra-space|distributing extra space]] as needed
to account for these items' minimum min-content contributions.
Clarified that 'grid-auto-rows' and 'grid-auto-columns' apply to
[=explicit grid tracks=] created by 'grid-template-areas'
that are not assigned a size by 'grid-template-rows' or 'grid-template-columns'.
(Issue 4914)
… These lines together with the explicit grid form the [=implicit grid=].
The 'grid-auto-rows' and 'grid-auto-columns' properties size these [=implicit grid tracks=],
as well as any [=explicit grid tracks=] created by 'grid-template-areas'
but not explicitly sized by 'grid-template-rows' or 'grid-template-columns'
The 'grid-auto-columns' and 'grid-auto-rows' properties specify
the size of such implicit tracks
tracks not assigned a size
by 'grid-template-rows' or 'grid-template-columns'.
If multiple track sizes are given, the pattern is repeated as necessary
to find the size of the implicitaffected tracks.
The first implicit grid track after the explicit grid
last explicitly-sized track
receives the first specified size, and so on forwards;
and the last implicit grid track before the explicit grid
receives the last specified size, and so on backwards.
Added reminder to track sizing algorithm
that gutters are treated as fixed-size tracks;
clarified their relationship to spanning items
(they are spanned by the same items as their lines, of course).
(Issue 2201)
For the purpose of [[#algo-track-sizing|track sizing]],
each gutter is treated as
an extra, empty, fixed-size track of the specified size,
which is spanned by any grid items
that span across its corresponding grid line.
Note: Remember that [[#gutters|gutters]] are treated as fixed-size tracks--
tracks with their min and max sizing functions both set to the gutter’s used size--
for the purpose of the grid sizing algorithm.
Their widths need to be incorporated into
the track sizing algorithm’s calculations accordingly.
Ensure that track sizes remain floored at zero during intrinsic sizing.
(Issue 2655)
grid-model/grid-gutters-and-tracks-001.html
More clearly defined computed value and animation type lines of each property,
particularly 'grid-template-rows' and 'grid-template-columns'.
(PR 3198,
Issue 3201)
Clarify the conditions for distributing space beyond growth limits
by clearly matching against the correct phases.
(Issue 3621)
when handling base sizes of tracks with ''min-content'' or ''auto'' minimums
accommodating minimum contributions
or accommodating min-content contributions:
any affected track that happens to also have an intrinsic max track sizing function;
if there are no such tracks, then all affected tracks.
when handling base sizes of tracks with ''max-content'' minimums
accommodating max-content contributions:
any affected track that happens to also have a ''max-content'' max track sizing function;
if there are no such tracks, then all affected tracks.
Clarify the cases where the minimum contribution
is taken from the minimum size.
(Issue 3612)
The minimum contribution of an item
is the smallest outer size it can have.
Specifically, it is the outer size
that would result from assuming
the item’s used minimum size
('min-width' or 'min-height', whichever matches the relevant axis)
as its preferred size
('width' or 'height', whichever matches the relevant axis)
if its computed preferred size [=behaves as auto=]
or depends on the size of the container in the relevant axis;
else is the item’s min-content contribution.
Because the minimum size often depends
on the size of the item’s content,
it is considered a type of intrinsic size contribution.
Clarified that blockification occurs
through intervening elements with ''display: contents'',
and does not consider whether the ''grid''/''inline-grid'' element
ends up actually generating a [=grid container=] box.
(Issue 4065)
The 'display' value of a grid item is blockified:
if the specified 'display' of an in-flow child of an element generating a grid container
is an inline-level value, it computes to its block-level equivalent.
If the [=computed value|computed=] 'display' value of an element's nearest ancestor element
(skipping ''display:contents'' ancestors)
is ''grid'' or ''inline-gird'',
the element's own 'display' value is [=blockified=].
Note: Blockification still occurs even when the ''display/flex'' or ''display/inline-flex'' element does not end up generating a [=flex container=] box,
e.g. when it is [=replaced element|replaced=]
or in a ''display: none'' subtree.
Added a reminder that the argument to ''fit-content()''
does not clamp the [=automatic minimum size=].
(Issue 4549)
The argument to ''fit-content()'' does not clamp
the [=content-based minimum size=] in the same way as a
fixedmax track sizing function.
Clarified antecedents for flexible tracks
in [[#algo-flex-tracks]].
The used flex fraction is the maximum of:
* For each flexible track, if the track’s flex factor is greater than one, the result of dividing the track’s base size by its flex factor; otherwise, the track’s base size.
* For each grid item that crosses a flexible track, the result of finding the size of an fr using all the grid tracks that the item crosses and a space to fill of the item’s max-content contribution.
Make initial calculation of |item-incurred increase| easier to read.
(Issue 5351)
Distribute space to base sizes up to growth limits:
Find the |item-incurred increase| for each spanned track with an affected size
by: distributing the space equally among such tracks,
freezing a track’s |item-incurred increase|
as its affected size + |item-incurred increase|
reaches its growth limit|limit|
(and continuing to grow the unfrozen tracks as needed).
If a track was marked as infinitely growable for this phase,
treat its growth limit as infinite for this calculation
(and then unmark it).
For [=base sizes=],
the |limit| is its [=growth limit=].
For [=growth limits=],
the |limit| is infinity if it is marked as [=infinitely growable=],
and equal to the [=growth limit=] otherwise.
Note: If the affected size was a growth limit
and the track is not marked [=infinitely growable=],
then each |item-incurred increase| will be zero.
Deferred subgrid feature to Level 2
due to lack of implementation and desire for further discussion.
(Issue 958)
Removed 'grid-row-gap' and 'grid-column-gap'
from the list of properties reset by the 'grid' shorthand.
(Issue 1036)
Removed 'grid-row-gap', 'grid-column-gap', and 'grid-gap' properties,
replacing with 'row-gap', 'column-gap', and 'gap'
which are now defined in CSS Box Alignment.
(Issue 1696)
Changed [[#grid-item-sizing|automatic sizing]]
of grid items (such as images) with an intrinsic size or ratio
so that they maintain their intrinsic size/ratio
whenever the alignment properties are ''align-self/normal'' (the default case).
(Issue #523)
See [[#grid-item-sizing]]
(vs. original).
Changed the behavior of <> tracks
inside a grid container whose size depends on the size of those tracks
to match implementations by
contributing their dimensions sized as ''grid-template-columns/auto''
and subsequently resolve the percentage against
the resulting grid container size
rather than being treated exactly as an ''grid-template-columns/auto'' track
or having their size and that of the grid container
increased from an ''grid-template-columns/auto'' size
in order to honor the percentage without overflow.
This will frequently result in tracks overflowing
the grid container
and in the contents of tracks overflowing the tracks
when <> sizes are used
in fit-content-sized grid containers
such as ''width/auto''-sized inline or floated grid containers.
(To avoid this problem, use <> units instead,
which are intended to maintain their ratios and not overflow
when the grid is intrinsically-sized.)
If the size of the grid container
depends on the size of its tracks,
then the <>
must be treated as auto
for the purpose of calculating the intrinsic sizes of the grid container
and then resolve against that size for the purpose of laying out the grid and its items.
The UA may adjust the intrinsic size contributions of the track
to the size of the grid container
and increase the final size of the track
by the minimum amount that would result in honoring the percentage.
Significant Adjustments and Fixes
Applied flex factor clamping to 1 also to indefinite case
(Issue 26,
see discussion):
Better integrated ''justify-content/stretch'' sizing of grid tracks
into the track sizing algorithm.
(Issue 1150, Issue 1866)
and the tracks are aligned within the grid container
according to the 'align-content' and 'justify-content' properties.
Note: This can introduce extra space within or between tracks.
When introducing space within tracks,
only tracks with an ''grid-template-rows/auto'' max track sizing function accept space.
This can introduce extra space between tracks,
potentially enlarging the grid area of any grid items spanning the gaps
beyond the space allotted to during track sizing.
If baseline alignment is specified on a grid item
whose size in that axis depends on the size of an intrinsically-sized track
(whose size is therefore dependent on both the item's size and baseline alignment,
creating a cyclic dependency),
that item does not participate in baseline alignment,
and instead uses its fallback alignment.
Shim baseline-aligned items
so their intrinsic size contributions reflect their baseline alignment.
For the items in each baseline-sharing group,
add a “shim” (effectively, additional margin)
on the start/end side (for first/last-baseline alignment)
of each item
so that,
when start/end-aligned together
their [[css-align-3#baseline-values|baselines align as specified]].
Consider these “shims” as part of the items’ intrinsic size contribution
for the purpose of track sizing, below.
If an item uses multiple intrinsic size contributions,
it can have different shims for each one.
Note: Note that both [[css-align-3#baseline-align-self|baseline self-aligned]]
and [[css-align-3#baseline-align-content|baseline content-aligned]] items
are considered in this step.
Note: Since grid items whose own size
depends on the size of an intrinsically-sized track
[[#row-align|do not participate in baseline alignment]],
they are not shimmed.
Adjusted [[#min-size-auto|automatic minimum size]] of grid items
to only trigger when spanning ''grid-template-columns/auto'' tracks
(Issue 12)
and ensured that this correctly affects the transferred size when the item has an aspect ratio
(Issue 11)
so that this implied minimum does not end up forcing overflow:
… the ''min-width/auto'' value of 'min-width'/'min-height'
also applies an automatic minimum size
in the specified axis
to grid items whose 'overflow' is ''overflow/visible''
and which span at least one track whose min track sizing function is ''grid-template-rows/auto''.
…
Adjusted [[#min-size-auto|automatic minimum size]] of grid items
to use the transferred size in preference to the content size,
rather than taking the smaller of the two.
(Issue #1149)
Fixed error in algorithm’s handling of ''grid-template-columns/auto'' min track sizes
where it didn't correctly handle max-content constraints;
and also made some editorial improvements.
(Issue 5)
Increase sizes to accommodate spanning items:
Next, consider the items with a span of 2
that do not span a track with a flexible sizing function,
treating a min track sizing function of ''auto''
as ''min-content''/''max-content''
when the grid container is being sized under a
min/max-content constraint (respectively):
Fixed error in distribute extra space algorithm,
where the accumulation was folded in per item rather than per track set;
and where it was not clear that distributed space per item
should be max()ed with the planned increase rather than added to it.
(Issue #1729)
For each considered item,
…
Distribute space to base sizes up to growth limits:Distribute the space equally to the planned increase of each spanned track with an affected size
Find the |item-incurred increase| for each spanned track with an affected size
by distributing the space equally among them,
freezing tracks as their size reaches their growth limit
(and continuing to grow the unfrozen tracks as needed).
…
Distribute space beyond growth limits:
If space remains after all tracks are frozen,
unfreeze and continue to distribute space to
the |item-incurred increase| of…
For each affected track,
if the track’s |item-incurred increase| is larger than the track’s |planned increase|
set the track’s |planned increase| to that value.
[numbering change from 2.4 to 3]
Update the tracks' affected sizes
by adding in the |planned increase|.
(If the affected size is an infinite growth limit,
set it to the track's base size plus the |planned increase|.)
Once the size of each grid area is thus established,
the grid items are laid out into their respective containing blocks.
The grid area’s width and height are considered definite for this purpose.
Note: Since formulas calculated using only definite sizes,
such as the stretch fit formula,
are also definite,
the size of a grid item which is stretched
is also considered definite.
If multiple track sizes are given, the pattern is repeated as necessary
to find the size of the implicit tracks.
The first implicit grid trackbefore after the explicit grid
receives the first specified size, and so on forwards;
and the last implicit grid track before the explicit grid
receives the last specified size, and so on backwards.
Clarifications
Clarified that ''fit-content()'' is not affected by ''align-content/stretch'' 'align-content'/'justify-content'.
(Issue 1732)
Represents the formula
min(''max-content'', max(''auto'', argument)),
which is calculated like similar to ''auto'' (i.e. ''minmax(auto, max-content)''),
except that the track size is clamped at argument
if it is greater than the ''auto'' minimum.
Otherwise,
set its base size
to the maximum of its items’ minimum contributions:.
The minimum contribution of an item is
the value specified by its respective outer size that would result from assuming
the item’s 'min-width' or 'min-height' value
(whichever matches the relevant axis)
as its specified size
if its specified size
('width' or 'height', whichever matches the relevant axis)
is ''width/auto'',
or else the item’s min-content contribution.
Alignment Subject(s):
The non-collapsedgrid tracks in the appropriate axis.
The grid tracks in the appropriate axis,
with any spacing inserted between tracks
added to the relevant gutters,
and treating collapsed gutters
as a single opportunity for space insertion.
Changed description of flexible length
to use “leftover space” instead of “free space”
to avoid mixing up concepts under the same name.
(Issue #1120)
Clarified that the [[#algo-grow-tracks|Maximize Tracks]] step
grows the base sizes of the tracks.
(Issue #1120)
If the free space is positive, distribute it equally
to the base sizes of all tracks,
freezing tracks as they reach their growth limits
(and continuing to grow the unfrozen tracks as needed).
Miscellaneous trivial fixes and minor editorial improvements.
Privacy and Security Considerations {#priv-sec}
===============================================
Grid introduces no new privacy leaks,
or security considerations beyond "implement it correctly".
