On 1/21/26 1:46 p.m., Chromestatus wrote:
*Contact emails*
[email protected], [email protected]
*Explainer*
/No information provided/
*Specification*
https://github.com/w3c/csswg-drafts/pull/11913/files
*Summary*
This proposal untangles ‘border-width’, ‘outline-width’, and
‘column-rule-width’ from their corresponding ‘*-style’ properties.
Previously, if a ‘*-style’ property, such as ‘border-style’, was set
to ‘none’ or ‘hidden’, the computed ‘*-width’, such as ‘border-width’,
would resolve to ‘0px’, even if the width was explicitly set to
‘10px’. Following a resolution in the CSSWG [1], the computed values
of ‘border-width’, ‘outline-width’, and ‘column-rule-width’ will now
reflect their specified values, regardless of the associated style
property's value. Similarly, the resolved values of ‘outline-width’,
and ‘column-rule-width’ will now reflect their specified values,
regardless of the associated style property's value. [1]:
https://github.com/w3c/csswg-drafts/issues/11494#issuecomment-2675800489
*Blink component*
Blink>CSS
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22>
*Web Feature ID*
/No information provided/
*Motivation*
Today, CSS special-cases ‘border-*-width’, ‘outline-width’, and
‘column-rule-width’ so that their computed value becomes ‘0px’ when
the corresponding ‘*-style’ is ‘none’ or ‘hidden’, even if the author
specified a nonzero width. With Gap Decorations extending
‘column-rule-*’ properties to support lists/repeaters, applying that
special-case becomes ambiguous and difficult to define consistently.
Having ‘*-width’ values independent of ‘*-style’, provides an
intuitive model for these properties and better reflects the
author-specified value.
As a non-CSS expert, can you help me better understand what "applying
that special-case becomes ambiguous and difficult to define
consistently"? Is this in terms of code that authors would write, or
prose for spec authors? An example would be helpful here.
*Initial public proposal*
https://github.com/w3c/csswg-drafts/issues/11494
*Search tags*
column-rule-width </features#tags:column-rule-width>, border-width
</features#tags:border-width>, outline-width
</features#tags:outline-width>
*TAG review*
/No information provided/
*TAG review status*
Not applicable
*Risks*
*Interoperability and Compatibility*
The interoperability risk is low as both Gecko and Webkit have already
implemented these changes. Compatibility risk is also low. The
resolved value for `border-width` via `getComputedStyle()` will remain
0px when `border-style` is set to `none`/ `hidden`, maintaining
backward compatibility. For `outline-width` and `column-rule-width`,
both computed and resolved values will show the specified values, as
these properties are rarely queried and unlikely to impact existing
content. To support the claim, we collected UseCounter data measuring
how often these values are queried. The computed‑value counters for
these properties are extremely low (<0.0001%). The resolved‑value
counters for ‘column-rule-width’ and ‘outline-width’ show ~2.37%
usage, which reflects calls to ‘getComputedStyle()’ rather than
observable rendering usage. Since ‘getComputedStyle()’ is frequently
queried by automated tooling (e.g. scrapers and fingerprinting
scripts) that do not depend on property semantics, this usage does not
indicate meaningful web‑facing reliance. As a result, the
compatibility risk remains low.
2.37% of page views is a lot of page views. Why do we feel confident
that border-width needs backwards compat considerations for
getComputedStyle but column-rule-width and outline-width don't? Are you
saying that 2.37% of the use counters are coming from fingerprinting?
I'm also not sure what it means for a scraper to trigger a UseCounter -
can you clarify? I've typically thought of scraping as a server-side
operation - are these web extensions?
thanks!
/Gecko/:
Shipped/Shipping (https://bugzilla.mozilla.org/show_bug.cgi?id=1998285)
/WebKit/:
Shipped/Shipping (https://bugs.webkit.org/show_bug.cgi?id=304940)
/Web developers/: No signals
/Other signals/:
*WebView application risks*
Does this intent deprecate or change behavior of existing APIs, such
that it has potentially high risk for Android WebView-based applications?
/No information provided/
*Debuggability*
No extra functionality is needed in Devtools to debug this feature
update.
*Will this feature be supported on all six Blink platforms (Windows,
Mac, Linux, ChromeOS, Android, and Android WebView)?*
Yes
*Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
Yes
https://wpt.fyi/results/css/css-backgrounds/animations/border-width-interpolation.html
https://wpt.fyi/results/css/CSS2/ui/outline-width-096.xht
https://wpt.fyi/results/css/CSS2/borders/border-width-011.xht
https://wpt.fyi/results/css/CSS2/borders/border-width-012.xht
https://wpt.fyi/results/css/css-ui/parsing/outline-width-computed.html
https://wpt.fyi/results/css/css-ui/outline-009.html
https://wpt.fyi/results/css/css-ui/animation/outline-width-interpolation.html
https://wpt.fyi/results/css/css-multicol/parsing/column-rule-width-computed.html
https://wpt.fyi/results/css/css-multicol/parsing/column-rule-computed.html
https://wpt.fyi/results/css/css-backgrounds/animations/border-width-interpolation.html
*Flag name on about://flags*
/No information provided/
*Finch feature name*
DecoupleComputedBorderWidthFromStyle,DecoupleResolvedColumnRuleWidthFromStyleEnabled
*Rollout plan*
Will ship enabled for all users
*Requires code in //chrome?*
False
*Tracking bug*
https://issues.chromium.org/issues/393631108
*Estimated milestones*
Shipping on desktop 146
Shipping on Android 146
Shipping on WebView 146
*Anticipated spec changes*
Open questions about a feature may be a source of future web compat or
interop issues. Please list open issues (e.g. links to known github
issues in the project for the feature specification) whose resolution
may introduce web compat/interop risk (e.g., changing to naming or
structure of the API in a non-backward-compatible way).
/No information provided/
*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5133099851317248?gate=5201902006173696
This intent message was generated by Chrome Platform Status
<https://chromestatus.com>.
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