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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang=en-US>
<head>
<title>Media Queries</title>
<style type="text/css">
blockquote {
background: #eef;
padding: 0.5em;
margin: 1em 0;
border: thin solid black; }
pre { font-family: courier, monospace; font-weight: bold; white-space: pre-wrap }
.example pre em { font-style: normal }
span.label { font-style: italic }
</style>
<link href="../default.css" rel=stylesheet>
<link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel=stylesheet>
<body>
<div class=head> <!--begin-logo-->
<p><a href="http://www.w3.org/"><img alt=W3C height=48
src="http://www.w3.org/Icons/w3c_home" width=72></a> <!--end-logo-->
<h1 id=media-queries>Media Queries</h1>
<h2 class="no-num no-toc" id=w3c-working>Editor's Draft 26 August 2009</h2>
<dl>
<dt>This Version:
<dd><a
href="http://www.w3.org/TR/2009/ED-css3-mediaqueries-20090826/">http://www.w3.org/TR/2009/ED-css3-mediaqueries-20090826/</a>
<dt>Latest Version:
<dd><a
href="http://www.w3.org/TR/css3-mediaqueries/">http://www.w3.org/TR/css3-mediaqueries/</a>
<dt>Latest Editor Version:
<dd><a
href="http://dev.w3.org/csswg/css3-mediaqueries/">http://dev.w3.org/csswg/css3-mediaqueries/</a>
<dt>Previous Version:
<dd><a
href="http://www.w3.org/TR/2008/WD-css3-mediaqueries-20081015/">http://www.w3.org/TR/2008/WD-css3-mediaqueries-20081015/</a>
<dt>Editors:
<dd class=vcard><a class="url fn n"
href="http://people.opera.com/howcome/" lang=no> <span
class=given-name>Håkon</span> <span
class=additional-name>Wium</span> <span class=family-name>Lie</span></a>
<<span class=email>howcome @opera.com</span>>
<dd class=vcard><a class="url fn" href="http://tantek.com/"
lang=tr>Tantek Çelik</a> <<span
class=email>tantek @cs.stanford.edu</span>>
<dd class=vcard><span class=given-name>Daniel</span> <span
class=family-name>Glazman</span> <<span
class=email>daniel.glazman @disruptive-innovations.com</span>>
<dd class=vcard><a class="url fn n" href="http://annevankesteren.nl/"
lang=nl>Anne van Kesteren</a> <<span
class=email>annevk@opera.com</span>>
</dl>
<!--begin-copyright-->
<p class=copyright><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright"
rel=license>Copyright</a> © 2009 <a
href="http://www.w3.org/"><acronym title="World Wide Web
Consortium">W3C</acronym></a><sup>®</sup> (<a
href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute
of Technology">MIT</acronym></a>, <a
href="http://www.ercim.org/"><acronym title="European Research Consortium
for Informatics and Mathematics">ERCIM</acronym></a>, <a
href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a
href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
and <a
href="http://www.w3.org/Consortium/Legal/copyright-documents">document
use</a> rules apply.</p>
<!--end-copyright-->
<hr title="Separator for header">
</div>
<h2 class="no-num no-toc" id=abstract>Abstract</h2>
<p>HTML4 and CSS2 currently support media-dependent style sheets tailored
for different <em>media types</em>. For example, a document may use
sans-serif fonts when displayed on a screen and serif fonts when printed.
‘<code class=css>screen</code>’ and ‘<code
class=css>print</code>’ are two media types that have been defined.
<em>Media queries</em> extend the functionality of media types by allowing
more precise labeling of style sheets.
<p>A media query consists of a media type and zero or more expressions to
limit the scope of style sheets. Among the <em>media features</em> that
can be used in media
93CD
queries are ‘<code
class=css>width</code>’, ‘<code
class=css>height</code>’, and ‘<code
class=css>color</code>’. By using media queries, presentations can
be tailored to a specific range of output devices without changing the
content itself.
<h2 class="no-num no-toc" id=status>Status of this document</h2>
<!--begin-status-->
<p>This is a public copy of the editors' draft. It is provided for
discussion only and may change at any moment. Its publication here does
not imply endorsement of its contents by W3C. Don't cite this document
other than as work in progress.
<p>The (<a
href="http://lists.w3.org/Archives/Public/www-style/">archived</a>) public
mailing list <a href="mailto:www-style@w3.org">www-style@w3.org</a> (see
<a href="http://www.w3.org/Mail/Request">instructions</a>) is preferred
for discussion of this specification. When sending e-mail, please put the
text “css3-mediaqueries” in the subject, preferably like this:
“[<!---->css3-mediaqueries<!---->] <em>…summary of
comment…</em>”
<p>This document was produced by the <a href="/Style/CSS/members">CSS
Working Group</a> (part of the <a href="/Style/">Style Activity</a>).
<p>This document was produced by a group operating under the <a
href="/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent
Policy</a>. W3C maintains a <a href="/2004/01/pp-impl/32061/status"
rel=disclosure>public list of any patent disclosures</a> made in
connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains <a
href="/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with <a
href="/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the
W3C Patent Policy</a>.</p>
<!--end-status-->
<!--
<p>This specification is a <strong>Last Call Working Draft</strong>. All
persons are encouraged to review this document and <strong>send comments
to the <a href="http://lists.w3.org/Archives/Public/www-style/">www-style</a>
mailing list</strong> as described above. The
<strong>deadline for comments</strong> is <strong>21 November 2008</strong>.</p>
-->
<p>For this specification to exit the CR stage, the following conditions
shall be met:
<ol>
<li>
<p>There must be at least two interoperable implementations. For the
purposes of this criterion, we define the following terms:</p>
<dl>
<dt>interoperable
<dd>
<p>passing the respective test case(s) in the <a
href="http://www.w3.org/Style/CSS/Test/">CSS test suite</a>, or, if
the implementation is not a Web browser, an equivalent test. Every
relevant test in the test suite should have an equivalent test created
if such a user agent (UA) is to be used to claim interoperability. In
addition if such a UA is to be used to claim interoperability, then
there must one or more additional UAs which can also pass those
equivalent tests in the same way for the purpose of interoperability.
The equivalent tests must be made publicly available for the purposes
of peer review.
<dt>implementation
<dd>
<p>a user agent which:</p>
<ol>
<li>implements the specification.
<li>is available (i.e. publicly downloadable or available through some
other public point of sale mechanism). This is the "show me"
requirement.
<li>is shipped, or is a "nightly build" (i.e., a development version
for the next release), but is not experimental (i.e., a version
specifically designed to pass the test suite and not intended for
daily usage going forward).
</ol>
</dl>
<li>
<p>There must be a Test Suite. (None available at the time of
publication.)
<li>
<p>A minimum of another six months of the CR period must elapse. That is,
this specification will not exit CR before 23 October 2009. When the
specification exits CR, an implementation report will be published. At
this point, no such report exists.
</ol>
<p>The <a
href="http://www.w3.org/Style/css3-updates/css3-mediaqueries-comments">comments
received on the last working draft</a> are still available.
<h2 class="no-num no-toc" id=contents>Table of contents</h2>
<!--begin-toc-->
<ul class=toc>
<li><a href="#background"><span class=secno>1 </span>Background</a>
<li><a href="#media0"><span class=secno>2 </span>Media Queries</a>
<li><a href="#syntax"><span class=secno>3 </span>Syntax</a>
<ul class=toc>
<li><a href="#error-handling"><span class=secno>3.1 </span>Error
Handling</a>
</ul>
<li><a href="#media1"><span class=secno>4 </span>Media features</a>
<ul class=toc>
<li><a href="#width"><span class=secno>4.1 </span>width</a>
<li><a href="#height"><span class=secno>4.2 </span>height</a>
<li><a href="#device-width"><span class=secno>4.3
</span>device-width</a>
<li><a href="#device-height"><span class=secno>4.4
</span>device-height</a>
<li><a href="#orientation"><span class=secno>4.5 </span>orientation</a>
<li><a href="#aspect-ratio"><span class=secno>4.6
</span>aspect-ratio</a>
<li><a href="#device-aspect-ratio"><span class=secno>4.7
</span>device-aspect-ratio</a>
<li><a href="#color"><span class=secno>4.8 </span>color</a>
<li><a href="#color-index"><span class=secno>4.9 </span>color-index</a>
<li><a href="#monochrome"><span class=secno>4.10 </span>monochrome</a>
<li><a href="#resolution"><span class=secno>4.11 </span>resolution</a>
<li><a href="#scan"><span class=secno>4.12 </span>scan</a>
<li><a href="#grid"><span class=secno>4.13 </span>grid</a>
</ul>
<li><a href="#values"><span class=secno>5 </span>Values</a>
<li><a href="#units"><span class=secno>6 </span>Units</a>
<ul class=toc>
<li><a href="#resolution0"><span class=secno>6.1 </span>Resolution</a>
</ul>
<li class=no-num><a href="#acknowledgments">Acknowledgments</a>
<li class=no-num><a href="#references">References</a>
<ul class=toc>
<li class=no-num><a href="#normative-references">Normative
references</a>
<li class=no-num><a href="#other-references">Other references</a>
</ul>
</ul>
<!--end-toc-->
<h2 id=background><span class=secno>1 </span>Background</h2>
<p>(This section is not normative.)
<p>HTML4 <a href="#HTML401" rel=biblioentry>[HTML401]<!--{{HTML401}}--></a>
and CSS2 <a href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
currently support media-dependent style sheets tailored for different
media types. For example, a document may use different style sheets for
screen and print. In HTML4, this can be written as:
<div class=example>
<pre>
<link rel="stylesheet" type="text/css" media="screen" href="sans-serif.css">
<link rel="stylesheet" type="text/css" media="print" href="serif.css">
</pre>
</div>
<p>Inside a CSS style sheet, one can declare that sections apply to certain
media types:
<div class=example>
<pre>
@media screen {
* { font-family: sans-serif }
}
</pre>
</div>
<p>The ‘<code class=css>print</code>’ and ‘<code
class=css>screen</code>’ media types are defined in HTML4. The
complete list of media types in HTML4 is: ‘<code
class=css>aural</code>’, ‘<code
class=css>braille</code>’, ‘<code
class=css>handheld</code>’, ‘<code
class=css>print</code>’, ‘<code
class=css>projection</code>’, ‘<code
class=css>screen</code>’, ‘<code class=css>tty</code>’,
‘<code class=css>tv</code>’. CSS2 defines the same list,
removes ‘<code class=css>aural</code>’ and adds ‘<code
class=css>embossed</code>’ and ‘<code
class=css>speech</code>’. Also, ‘<code
class=css>all</code>’ is used to indicate that the style sheet
applies to all media types.
<p>Media-specific style sheets are supported by several user agents. The
most commonly used feature is to distinguish between ‘<code
class=css>screen</code>’ and ‘<code
class=css>print</code>’.
<p>There have been requests for ways to describe in more detail what type
of output devices a style sheet applies to. Fortunately HTML4 foresaw
these requests and defined a forward-compatible syntax for media types.
Here is a quote from <a
href="http://www.w3.org/TR/1999/REC-html401-19991224/types.html#h-6.13">HTML4,
section 6.13</a>:
<blockquote
cite="http://www.w3.org/TR/1999/REC-html401-19991224/types.html#h-6.13">
<p>Future versions of HTML may introduce new values and may allow
parameterized values. To facilitate the introduction of these extensions,
conforming user agents must be able to parse the <a
href="http://www.w3.org/TR/1999/REC-html401-19991224/present/styles.html#adef-media"><samp>media</samp></a>
attribute value as follows:
<ol>
<li>The value is a comma-separated list of entries. For example,
<pre>
media="screen, 3d-glasses, print and resolution > 90dpi"
</pre>
<p>is mapped to:</p>
<pre>
"screen"
"3d-glasses"
"print and resolution > 90dpi"
</pre>
<li>Each entry is truncated just before the first character that isn't a
US ASCII letter [a-zA-Z] (Unicode decimal 65-90, 97-122), digit [0-9]
(Unicode hex 30-39), or hyphen (45). In the example, this gives:
<pre>
"screen"
"3d-glasses"
"print"
</pre>
</ol>
</blockquote>
<p>Media queries, as described in this specification, build on the
mechanism outlined in HTML4. The syntax of media queries fit into the
media type syntax reserved in HTML4. The <code class=html>media</code>
attribute of HTML4 also exists in XHTML and generic XML. The same syntax
can also be used inside in the ‘<code class=css>@media</code>’
and ‘<code class=css>@import</code>’ rules of CSS.
<p>However, the parsing rules for media queries are incompatible with those
of HTML4 so that they are consistent with those of media queries used in
CSS. It is expected that future versions of HTML refer to the media
queries specification directly so that this difference is resolved.
<h2 id=media0><span class=secno>2 </span>Media Queries</h2>
<p>A media query consists of a media type and zero or more <span
class=index id=expressions>expressions</span> involving <span class=index
id=media-features>media features</span>. If the media type is omitted it
is assumed to be ‘<code class=css>all</code>’.
<p>Statements regarding media queries in this section assume the <a
href="#syntax">syntax section</a> is followed. Media queries that do not
conform to the syntax are discussed in the <a href="#error-handling">error
handling section</a>. I.e. the syntax takes precedence over requirements
in this section.
<div class=example>
<p>Here is a simple example written in HTML:</p>
<pre>
<span class=html-example><link rel="stylesheet" media="screen and (color)" href="example.css" /></span>
</pre>
<p>This example expresses that a certain style sheet
(<code>example.css</code>) applies to devices of a certain media type
(‘<code class=css>screen</code>’) with certain feature (it
must be a color screen).</p>
<p class=note>HTML has not yet been normatively updated to use media
queries in the <code>media</code> attribute.</p>
</div>
<div class=example>
<p>Here the same media query written in an @import-rule in CSS:</p>
<pre>
<span class=css-example>@import url(color.css) screen and (color);</span>
</pre>
</div>
<p>A media query is a logical expression that is either true or false. A
media query is true if the media type of the media query matches the media
type of the device where the user agent is running (as defined in the
"Applies to" line), and all expressions in the media query are true. Also,
a media query which is otherwise false becomes true if the ‘<code
class=css>not</code>’ keyword is present.
<p>When a media query is true, the corresponding style sheet is applied as
per the normal cascading rules.
<p>Several media queries can be combined in a comma-separated list. If one
or more of the media queries in the comma-separated list is true, the
associated style sheet is applied, otherwise the associated style sheet is
ignored.
<div class=example>
<p>Here is an example of several media queries in a comma-separated list
using the an @media-rule in CSS:</p>
<pre>
<span class=css-example>@media <em>screen and (color), projection and (color)</em> { ... }</span>
</pre>
</div>
<p>In the media queries syntax, the comma expresses a logical OR, while the
‘<code class=css>and</code>’ keyword expresses a logical AND.
<p>The logical NOT can be expressed through the ‘<code
class=css>not</code>’ keyword.
<div class=example>
<pre>
<span class=html-example><link rel="stylesheet" media="<em>not screen and (color)</em>" href="example.css" /></span>
</pre>
</div>
<p>The presence of the keyword ‘<code class=css>not</code>’ at
the beginning of the query negates the result. I.e., if the media query
had been true without the ‘<code class=css>not</code>’ keyword
it will become false, and vice versa. User agents that only support media
types (as described in HTML4) will not recognize the ‘<code
class=css>not</code>’ keyword and the associated style sheet is
therefore not applied.
<p>The keyword ‘<code class=css>only</code>’ can also be used
to hide style sheets from older user agents. User agents must process
media queries starting with ‘<code class=css>only</code>’ as
if the ‘<code class=css>only</code>’ keyword was not present.
<div class=example>
<pre>
<span class=html-example><link rel="stylesheet" media="<em>only screen and (color)</em>" href="example.css" /></span>
</pre>
</div>
<p>The media queries syntax can be used with HTML, XHTML, XML <a
href="#XMLSTYLE" rel=biblioentry>[XMLSTYLE]<!--{{XMLSTYLE}}--></a> and the
@import and @media rules of CSS.
<div class=example>
<p>Here is the same example written in HTML, XHTML, XML, @import and
@media:</p>
<pre>
<span class=html-example><link rel="stylesheet" media="<em>screen and (color), projection and (color)</em>" rel="stylesheet" href="example.css"></span>
<span class=html-example><link rel="stylesheet" media="<em>screen and (color), projection and (color)</em>" rel="stylesheet" href="example.css" /></span>
<span class=xml-example><?xml-stylesheet media="<em>screen and (color), projection and (color)</em>" rel="stylesheet" href="example.css" ?></span>
<span class=css-example>@import url(example.css) screen and (color), projection and (color);</span>
<span class=css-example>@media screen and (color), projection and (color) { ... }</span>
</pre>
<p class=note>Just like HTML, the <a href="#XMLSTYLE"
rel=biblioentry>[XMLSTYLE]<!--{{XMLSTYLE}}--></a> specification has not
yet been updated to use media queries in the <code>media</code>
pseudo-attribute.</p>
</div>
<p>If a media feature does not apply to the device where the UA is running,
expressions involving the media feature will be false.
<div class=example>
<p>The media feature ‘<code
class=css>device-aspect-ratio</code>’ only applies to visual
devices. On an aural device, expressions involving ‘<code
class=css>device-aspect-ratio</code>’ will therefore always be
false:</p>
<pre>
<span class=html-example><link rel="stylesheet" media="aural and (device-aspect-ratio: 16/9)" href="example.css" /></span>
</pre>
</div>
<p>Expressions will always be false if the unit of measurement does not
apply to the device.
<div class=example>
<p>The ‘<code class=css>px</code>’ unit does not apply to
‘<code class=css>speech</code>’ devices so the following
media query is always false:</p>
<pre>
<span class=html-example><link rel="stylesheet" media="speech and (min-device-width: 800px)" href="example.css" /></span>
</pre>
<p>Note that the media queries in this example would have been true if the
keyword ‘<code class=css>not</code>’ had been added to the
beginning of the media query.</p>
</div>
<p>A shorthand syntax is offered for media queries that apply to all media
types; the keyword ‘<code class=css>all</code>’ can be left
out (along with the trailing ‘<code class=css>and</code>’).
<div class=example>
<p>These two media queries are equivalent:</p>
<pre>
@media all and (orientation: portrait) { ... }
@media (orientation: portrait) { ... }
</pre>
</div>
<p>To avoid circular dependencies, it is never necessary to apply the style
sheet in order to evaluate expressions. For example, the aspect ratio of a
printed document may be influenced by a style sheet, but expressions
involving ‘<code class=css>device-aspect-ratio</code>’ will be
based on the default aspect ratio of the user agent.
<p class=note>User agents are expected, but not required, to re-evaluate
and re-layout the page in response to changes in the user environment, for
example if the device is tilted from landscape to portrait mode.
<h2 id=syntax><span class=secno>3 </span>Syntax</h2>
<p>The media query syntax is described in terms of the <a
href="http://www.w3.org/TR/CSS21/grammar.html">CSS2 grammar</a>. As such,
rules not defined here are defined in CSS2. The
<code>media_query_list</code> production defined below replaces the
<code>media_list</code> production from CSS2. <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<pre>media_query_list
: S* media_query [ ',' S* media_query]*
;
media_query
: [ONLY | NOT]? S* media_type S* [ AND S* expression ]*
| expression [ AND S* expression ]*
;
media_type
: IDENT
;
expression
: '(' S* media_feature S* [':' S* expr]? ')' S*
;
media_feature
: IDENT
;</pre>
<p>COMMENT tokens, as defined by CSS2, do not occur in the grammar (to keep
it readable), but any number of these tokens may appear anywhere between
other tokens. <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<p>The following new definitions are introduced:
<pre>
L l|\\0{0,4}(4c|6c)(\r\n|[ \t\r\n\f])?|\\l
Y y|\\0{0,4}(59|79)(\r\n|[ \t\r\n\f])?|\\y</pre>
<p>The following new tokens are introduced:
<pre>
{O}{N}{L}{Y} {return ONLY;}
{N}{O}{T} {return NOT;}
{A}{N}{D} {return AND;}
{num}{D}{P}{I} {return RESOLUTION;}
{num}{D}{P}{C}{M} {return RESOLUTION;}</pre>
<p><code>RESOLUTION</code> is to be added to the CSS2 <code>term</code>
production.
<p>CSS style sheets are generally case-insensitive, and this is also the
case for media queries.
<p>In addition to conforming to the syntax, each media query needs to use
media types and media features according to their respective specification
in order to be considered conforming.
<div class=example>
<p>Only the first media query is conforming in the example below because
the "example" media type does not exist.</p>
<pre>
@media all { body { background:lime } }
@media example { body { background:red } }
</pre>
</div>
<h3 id=error-handling><span class=secno>3.1 </span>Error Handling</h3>
<p>For media queries that are not conforming user agents need to follow the
rules described in this section.
<ul>
<li>
<p><strong>Unknown media types.</strong> Unknown media types evaluate to
false. Effectively, they are treated identically to known media types
that do not match the media type of the device.</p>
<div class=example>
<p>The media query "<code>unknown</code>" will evaluate to false, unless
<code>unknown</code> is actually a supported media type. Similarly,
"<code>not unknown</code>" will evaluate to true.</p>
</div>
<p class=note>Unknown media types are distinct from media types that do
not actually match the IDENT production. Those fall under the malformed
media query clause.</p>
<li>
<p><strong>Unknown media features.</strong> User agents are to ignore a
media query when one of the specified media features is unknown.</p>
<div class=example>
<pre><span class=html-example><link rel="stylesheet" media="screen and (max-weight: 3kg) and (color), (color)" href="example.css" /></span></pre>
<p>In this example, the first media query is rejected due to an unknown
media feature and unknown value, but the second media query is
evaluated as if the first had not been specified.</p>
</div>
<div class=example>
<pre>@media (min-orientation:portrait) { ... }</pre>
<p>Is dropped because the ‘<code
class=css>orientation</code>’ feature does not accept the
‘<code class=css>min-</code>’ prefix.
</div>
<li>
<p><strong>Unknown media feature values.</strong> As with unknown media
features, user agents are to ignore a media query when one of the
specified media feature values is unknown.</p>
<div class=example>
<p>The media query <code>(color:20example)</code> specifies an unknown
value for the ‘<code class=css>color</code>’ media feature
and is therefore ignored.</p>
</div>
<div class=example>
<p>This media query is invalid because negative lengths are not allowed
for the ‘<code class=css>width</code>’ media feature:
<pre>@media (min-width: -100px) { ... }</pre>
</div>
<li>
<p><strong>Malformed media query.</strong> User agents are to handle
unexpected tokens encountered while parsing a media query by reading
until the end of the media query, while observing <a
href="http://www.w3.org/TR/CSS21/syndata.html#block">the rules for
matching pairs</a> of (), [], {}, "", and '', and correctly handling
escapes. Media queries with unexpected tokens are ignored. <a
href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>
<div class=example>
<pre>@media (example, all,), speech { /* only applicable to speech devices */ }
@media &test, screen { /* only applicable to screen devices */ }</pre>
</div>
<div class=example>
<p>The following is an malformed media query because having no space
between ‘<code class=css>and</code>’ and the expression is
not allowed. (That is reserved for the functional notation syntax.)</p>
<pre>@media all and(color) { ... }</pre>
</div>
<p>When all media queries in a media query list are ignored it is the
same as if "<code>not all</code>" was specified.</p>
<div class=example>
<p>The following lists of media queries would all end up as "<code>not
all</code>":</p>
<pre>@media test, @test { ... }
@media example { ... }
@media screen and (min-example), example { ...}</pre>
</div>
<p>Media queries are expected to follow the error handling rules of the
host language as well.</p>
<div class=example>
<pre>@media test;,all { body { background:lime } }</pre>
<p>… will not apply because the semicolon terminates the
<code>@media</code> rule in CSS.</p>
</div>
</ul>
<h2 id=media1><span class=secno>4 </span>Media features</h2>
<p>Syntactically, media features resemble CSS properties: they have names
and accept certain values. There are, however, several important
differences between properties and media features:
<ul>
<li>Properties are used in <em>declarations</em> to give information about
how to present a document. Media features are used in
<em>expressions</em> to describe requirements of the output device.
<li>Most media features accept optional ‘<code
class=css>min-</code>’ or ‘<code class=css>max-</code>’
prefixes to express "greater or equal to" and "smaller or equal to"
constraints. This syntax is used to avoid "<" and ">" characters
which may confl
1337
ict with HTML and XML. Those media features that accept
prefixes will most often be used with prefixes, but can also be used
alone.
<li>Properties always require a value to form a declaration. Media
features, on the other hand, can also be used without a value. For a
media feature <var>feature</var>, <code>(<var>feature</var>)</code> will
evaluate to true if <code>(<var>feature</var>:<var>x</var>)</code> will
evaluate to true for a value <var>x</var> other than zero or zero
followed by a unit identifier (i.e., other than <code>0</code>,
<code>0px</code>, <code>0em</code>, etc.). Media features that are
prefixed by min/max cannot be used without a value. When a media feature
prefixed with min/max is used without a value it makes the media query
malformed.
<li>Properties may accept more complex values, e.g., calculations that
involve several other values. Media features only accept single values:
one keyword, one number, or a number with a
6D57
unit identifier. (The only
exceptions are the ‘<code class=css>aspect-ratio</code>’ and
‘<code class=css>device-aspect-ratio</code>’ media features.)
</ul>
<div class=example>
<p>For example, the ‘<code class=css>color</code>’ media
feature can form expressions without a value (‘<code
class=css>(color)</code>’), or with a value (‘<code
class=css>(min-color: 1)</code>’).</p>
</div>
<p class=note>This specification defines media features usable with visual
and tactile devices. Similarly, media features can be defined for aural
media types.
<h3 id=width><span class=secno>4.1 </span>width</h3>
<div class=media-feature><span class=label>Value:</span> <length><br>
<span class=label>Applies to:</span> visual and tactile media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>width</code>’ media feature describes
the width of the targeted display area of the output device. For
continuous media, this is the width of the viewport (as described by CSS2,
section 9.1.1 <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>) including the size of a
rendered scroll bar (if any). For paged media, this is the width of the
page box (as described by CSS2, section 13.2 <a href="#CSS21"
rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>).
<p>A specified <length> cannot be negative.
<div class=example>
<p>For example, this media query expresses that the style sheet is usable
on printed output wider than 25cm:</p>
<pre>
<span class=html-example><link rel="stylesheet" media="print and (min-width: 25cm)" href="http://...." /></span>
</pre>
</div>
<div class=example>
<p>This media query expresses that the style sheet is usable on devices
with viewport (the part of the screen/paper where the document is
rendered) widths between 400 and 700 pixels:</p>
<pre>
<span class=css-example>@media screen and (min-width: 400px) and (max-width: 700px) { ... }</span>
</pre>
</div>
<div class=example>
<p>This media query expresses that style sheet is usable on screen and
handheld devices if the width of the viewport is greater than 20em.</p>
<pre>
<span class=css-example>@media handheld and (min-width: 20em),
screen and (min-width: 20em) { ... }</span>
</pre>
<p>The ‘<code class=css>em</code>’ value is relative to the
font size of the root element.</p>
</div>
<h3 id=height><span class=secno>4.2 </span>height</h3>
<div class=media-feature><span class=label>Value:</span> <length><br>
<span class=label>Applies to:</span> visual and tactile media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>height</code>’ media feature describes
the height of the targeted display area of the output device. For
continuous media, this is the height of the viewport including the size of
a rendered scroll bar (if any). For paged media, this is the height of the
page box.
<p>A specified <length> cannot be negative.
<h3 id=device-width><span class=secno>4.3 </span>device-width</h3>
<div class=media-feature><span class=label>Value:</span> <length><br>
<span class=label>Applies to:</span> visual and tactile media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>device-width</code>’ media feature
describes the width of the rendering surface of the output device. For
continuous media, this is the width of the screen. For paged media, this
is the width of the page sheet size.
<p>A specified <length> cannot be negative.
<div class=example>
<pre>
<span class=css-example>@media screen and (device-width: 800px) { ... }</span>
</pre>
<p>In the example above, the style sheet will apply only to screens that
currently displays exactly 800 horizontal pixels. The ‘<code
class=css>px</code>’ unit is of the logical kind, as described in
the <a href="#units">Units</a> section.</p>
</div>
<h3 id=device-height><span class=secno>4.4 </span>device-height</h3>
<div class=media-feature><span class=label>Value:</span> <length><br>
<span class=label>Applies to:</span> visual and tactile media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>device-height</code>’ media feature
describes the height of the rendering surface of the output device. For
continuous media, this is the height of the screen. For paged media, this
is the height of the page sheet size.
<p>A specified <length> cannot be negative.
<div class=example>
<pre>
<span class=html-example><link rel="stylesheet" media="screen and (device-height: 600px)" /></span>
</pre>
<p>In the example above, the style sheet will apply only to screens that
have exactly 600 vertical pixels. Note that the definition of the
‘<code class=css>px</code>’ unit is the same as in other
parts of CSS.</p>
</div>
<h3 id=orientation><span class=secno>4.5 </span>orientation</h3>
<div class=media-feature><span class=label>Value:</span> portrait |
landscape<br>
<span class=label>Applies to:</span> bitmap media types<br>
<span class=label>Accepts min/max prefixes:</span> no<br>
</div>
<p>The ‘<code class=css>orientation</code>’ media feature is
‘<code class=css>portrait</code>’ when the value of the
‘<code class=css>height</code>’ media feature is greater than
or equal to the value of the ‘<code class=css>width</code>’
media feature. Otherwise ‘<code class=css>orientation</code>’
is ‘<code class=css>landscape</code>’.
<div class=example>
<pre>
@media all and (orientation:portrait) { ... }
@media all and (orientation:landscape) { ... }
</pre>
</div>
<h3 id=aspect-ratio><span class=secno>4.6 </span>aspect-ratio</h3>
<div class=media-feature><span class=label>Value:</span> <ratio><br>
<span class=label>Applies to:</span> bitmap media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>aspect-ratio</code>’ media feature is
defined as the ratio of the value of the ‘<code
class=css>width</code>’ media feature to the value of the
‘<code class=css>height</code>’ media feature.
<h3 id=device-aspect-ratio><span class=secno>4.7 </span>device-aspect-ratio</h3>
<div class=media-feature><span class=label>Value:</span> <ratio><br>
<span class=label>Applies to:</span> bitmap media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>device-aspect-ratio</code>’ media
feature is defined as the ratio of the value of the ‘<code
class=css>device-width</code>’ media feature to the value of the
‘<code class=css>device-height</code>’ media feature.
<div class=example>
<p>For example, if a screen device with square pixels has 1280 horizontal
pixels and 720 vertical pixels (commonly referred to as "16:9"), the
following Media Queries will all match the device:</p>
<pre>
<span class=css-example>@media screen and (device-aspect-ratio: 16/9) { ... }
@media screen and (device-aspect-ratio: 32/18) { ... }
@media screen and (device-aspect-ratio: 1280/720) { ... }
@media screen and (device-aspect-ratio: 2560/1440) { ... }</span>
</pre>
</div>
<h3 id=color><span class=secno>4.8 </span>color</h3>
<div class=media-feature><span class=label>Value:</span>
<integer><br>
<span class=label>Applies to:</span> visual media types<br>
<span class=label>Accept min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>color</code>’ media feature describes
the number of bits per color component of the output device. If the device
is not a color device, the value is zero.
<p>A specified <integer> cannot be negative.
<div class=example>
<p>For example, these two media queries express that a style sheet applies
to all color devices:</p>
<pre>
<span class=css-example>@media all and (color) { ... }
@media all and (min-color: 1) { ... }</span>
</pre>
</div>
<div class=example>
<p>This media query expresses that a style sheet applies to color devices
with 2 or more bits per color component:</p>
<pre>
<span class=css-example>@media all and (min-color: 2) { ... }</span>
</pre>
</div>
<p>If different color components are represented by different number of
bits, the smallest number is used.
<div class=example>
<p>For instance, if an 8-bit color system represents the red component
with 3 bits, the green component with 3 bits and the blue component with
2 bits, the ‘<code class=css>color</code>’ media feature will
have a value of 2.</p>
</div>
<p>In a device with indexed colors, the minimum number of bits per color
component in the lookup table is used.
<p class=note>The described functionality is only able to describe color
capabilities at a superficial level. If further functionality is required,
RFC2531 <a href="#RFC2531" rel=biblioentry>[RFC2531]<!--{{RFC2531}}--></a>
provides more specific media features which may be supported at a later
stage.
<h3 id=color-index><span class=secno>4.9 </span>color-index</h3>
<div class=media-feature><span class=label>Value:</span>
<integer><br>
<span class=label>Applies to:</span> visual media types<br>
<span class=label>Accepts min/max prefixes:</span> yes<br>
</div>
<p>The ‘<code class=css>color-index</code>’ media feature