*Contact emails*
[email protected]

*Specification*
https://www.w3.org/TR/css-typed-om-1/#stylevalue-subclasses

*Summary*
The CSS Typed OM spec exposes the CSSStyleValue hierarchy to worker global scopes ([Exposed=(Window, Worker, PaintWorklet, LayoutWorklet)]), but Blink only exposed CSSStyleValue, CSSKeywordValue, CSSNumericValue, CSSUnitValue and CSSUnparsedValue to Window and the worklets. As a result these constructors were undefined in Workers, unlike in Firefox and Safari.

*Blink component*
Blink>CSS <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22>

*Web Feature ID*
css-typed-om <https://webstatus.dev/features/css-typed-om>

*Motivation*
Aligns Chrome with the spec's [Exposed] set and removes a cross‑thread inconsistency (these constructors are currently undefined in workers); enables off‑main‑thread CSS value manipulation

*Initial public proposal*
/No information provided/

*TAG review*
/No information provided/

*TAG review status*
Not applicable

*Goals for experimentation*
None

*Risks*


*Interoperability and Compatibility*
This feature is already shipped by Firefox and Safari and it's purely additive worker‑scope exposure; zero change to existing Window behavior; matches the spec. Only theoretical risk: content that feature‑detects these globals inside a worker

/Gecko/: Shipped/Shipping

/WebKit/: Shipped/Shipping

/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 special tooling; interfaces work in the worker DevTools console like any other worker‑exposed API

*Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?*
Yes

*Is this feature fully tested byweb-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
Yes
css/css-typed-om/stylevalue-subclasses/*.any.js (global=window,worker): cssKeywordValue, cssKeywordValue-value, cssUnparsedValue-empty, numeric-objects/cssUnitValue-to; and (full‑scope) the converted create-a-type, cssMathInvert-type, cssMathNegate-type, add-two-types, cssnumericvalue-multiply-two-types, arithmetic, to .any.js. (The CSSMath* ones require the full‑scope exposure.)https://wpt.fyi/results/css/css-typed-om/stylevalue-subclasses?label=experimental&label=master&aligned <https://wpt.fyi/results/css/css-typed-om/stylevalue-subclasses?label=experimental&label=master&aligned>

*Flag name on about://flags*
/No information provided/

*Finch feature name*
/No information provided/

*Non-finch justification*
This is just a minor CSS change to allow some CSS javascript bindings to be run in Worker context, but that were already exposed to the Web via Window context.

*Rollout plan*
Will ship enabled for all users

*Requires code in //chrome?*
False

*Tracking bug*
https://issues.chromium.org/issues/534781956

*Estimated milestones*
Shipping on desktop     153
Shipping on Android     153
Shipping on WebView     153



*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).

https://github.com/w3c/csswg-drafts/issues/14229

*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5114591051907072?gate=6116938171416576

This intent message was generated byChrome Platform Status <https://chromestatus.com/>.

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