[css-text-decor] What to do with `blink` value in `text-decoration`?

[nt1m]

It's not shipping in Blink or WebKit and it's already deprecated. There's no reason to keep it around anymore.

[schenney-chromium]

Absolutely. Can we async resolve on this?

[fantasai]

No, we can't remove it, because that would make declarations like text-decoration: blink underline invalid. At least now they are underlined.

[nt1m]

They're already invalid in Blink and WebKit... I'm not convinced compat is a good argument here

[fantasai]

Testcase

[nt1m]

Ah, I was mislead by the WPT results then :( It would maybe be good still to clarify how blink serializes?

[schenney-chromium]

Searching all of github reveals 2 projects using text-decoration: blink [over/under]line

A httparchive query on the httparchive.almanac.parsed_css table for any text-decoration: *blink* gives the table below in json format.

It would take a bit more work to figure out which sites combine blink with something else valid, but 2500ish sites may not be enough reason to keep blink around.

[{
"value": "blink",
"freq": "179204"
}, {
"value": "blink !important",
"freq": "2948"
}, {
"value": "underline blink",
"freq": "1452"
}, {
"value": "blink!important",
"freq": "1448"
}, {
"value": "2px overline underline blink #3c883c",
"freq": "346"
}, {
"value": "overline blink",
"freq": "325"
}, {
"value": "blink underline",
"freq": "231"
}, {
"value": "underline overline blink",
"freq": "216"
}, {
"value": "line-through blink",
"freq": "97"
}, {
"value": "underline, blink",
"freq": "84"
}, {
"value": "none blink",
"freq": "55"
}, {
"value": "underline overline line-through blink",
"freq": "45"
}, {
"value": "blinker",
"freq": "43"
}, {
"value": "underline overline blink none",
"freq": "39"
}, {
"value": "blink ",
"freq": "24"
}, {
"value": "\u0027blink\u0027",
"freq": "17"
}, {
"value": "underline,blink",
"freq": "16"
}, {
"value": "blink, underline",
"freq": "15"
}, {
"value": "underline blink !important",
"freq": "15"
}, {
"value": "overline underline blink",
"freq": "14"
}, {
"value": "blink blink",
"freq": "14"
}, {
"value": "blinks",
"freq": "12"
}, {
"value": "blink underline dotted",
"freq": "12"
}, {
"value": "inherit blink",
"freq": "10"
}, {
"value": "underline blink?, OffX\u003d?, OffY\u003d?, Positive\u003d?)",
"freq": "9"
}, {
"value": "none|underline,blink",
"freq": "9"
}, {
"value": "blinking",
"freq": "8"
}, {
"value": "blinka",
"freq": "8"
}, {
"value": "blink !Important",
"freq": "8"
}, {
"value": "blink line-through",
"freq": "8"
}, {
"value": "bold,blink",
"freq": "8"
}, {
"value": "none, blink",
"freq": "8"
}, {
"value": "blinker2",
"freq": "6"
}, {
"value": "blink underline overline",
"freq": "6"
}, {
"value": "blink2",
"freq": "6"
}, {
"value": "blink underline overline!important",
"freq": "5"
}, {
"value": "TermometroUSB_blink",
"freq": "5"
}, {
"value": "bold underline blink",
"freq": "5"
}, {
"value": "blink-webkit-animation-name:blinker",
"freq": "5"
}, {
"value": "\u0027underline\u0027,\u0027blink\u0027",
"freq": "4"
}, {
"value": "blink?, Direction\u003d?, Strength\u003d?)",
"freq": "2"
}, {
"value": "SHARP, blink",
"freq": "2"
}, {
"value": "underline/blink/",
"freq": "2"
}, {
"value": "blink auto!important",
"freq": "2"
}, {
"value": "text-decoration: blink",
"freq": "2"
}, {
"value": "blink ! important",
"freq": "2"
}, {
"value": "blink none",
"freq": "2"
}, {
"value": "blinker-neon",
"freq": "2"
}, {
"value": "blink,color:#314754",
"freq": "2"
}, {
"value": "underline , blink",
"freq": "2"
}, {
"value": "blink,none",
"freq": "2"
}, {
"value": "line-through,overline,blink,underline",
"freq": "2"
}, {
"value": "blink,underline",
"freq": "2"
}, {
"value": "blink underline overline !important",
"freq": "2"
}, {
"value": "[ blink || overline ] | inherit",
"freq": "2"
}, {
"value": "\u0027underline|blink\u0027",
"freq": "2"
}, {
"value": "blink-text",
"freq": "1"
}, {
"value": "blink color : #0000ff",
"freq": "1"
}, {
"value": "line-through,blink",
"freq": "1"
}, {
"value": "blink -webkit-animation-name:blinker",
"freq": "1"
}, {
"value": "underline | blink",
"freq": "1"
}, {
"value": "\u0027blink\u0027,\u0027underline\u0027",
"freq": "1"
}, {
"value": "blink #FC0",
"freq": "1"
}]

[frivoal]

The spec already allows UAs not to blink when that value is used. Surely we would not introduce it today, but we have interop on parsing it and on not blinking.

I think we could update the spec to say you're not supposed to do anything when this value is specified, but it makes sense to me to keep supporting it, so that when it is combined with other values, it keeps parsing.

[tabatkins]

Yeah, just a quick

For legacy purposes, implementations must also support the blink keyword, which has no effect.

[mdubet]

What should be the computed value when blink is specified ? Engines disagree.

https://wpt.fyi/results/css/css-text-decor/parsing/text-decoration-line-computed.html?label=master&label=experimental&aligned&view=interop&q=label%3Ainterop-2025-textdecoration

[frivoal]

In summary:

1. blink doesn't do anything beyond parsing in any browser

2. currently, Firefox takes underline blink and computes to / inherits as underline blink, while Chrome and Safari simplify it to just underline:

   https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=13926

3. This simplification is happening at computed value time, because all three browsers preserve underline blink in the specified value:

   https://software.hixie.ch/utilities/js/live-dom-viewer/?saved=13927

Currently, the definition of blink is this: https://drafts.csswg.org/css-text-decor-4/#valdef-text-decoration-line-blink

The text blinks (alternates between visible and invisible). Conforming user agents may simply not blink the text. Note that not blinking the text is one technique to satisfy checkpoint 3.3 of WAI-UAAG. This value is deprecated in favor of Animations [CSS3-ANIMATIONS].

If we want the Firefox behavior, the definition of the blink keyword could be something like:

This legacy value must be supported for parsing purposes, but has no effect.

If we want the Chrome/Safari behavior, we might expand it to something like:

This legacy value must be supported for parsing purposes, but has no effect.
If specified alone, the blink keyword computes to none.
If specified in combination with one or more other keywords, the blink keyword is dropped from the computed value.

[astearns]

Does this need to stay in the agenda queue? Could we resolve async on the computed value question?

[nt1m]

(also should we retitle this issue to be about serialization if we're not going to unship blink?)

[frivoal]

There are two questions, not one:

• do we want to switch from "may" have no effect to "must" have no effect?
• do we want to match Firefox (no computed value simplification) or Chrome/Safari (blink computes away)?

The first one is a very likely yes, and could easily be resolved async. The second one is also not very complex, and may be doable async too, but at this point, other than just counting implementations, I don't have a good sense of what is the preferred resolution.

[nt1m]

I'd prefer having blink compute away, so we can just make it a parse-time hack instead of keeping the value stored around