LGTM3 On Fri, Mar 13, 2026 at 6:21 AM Mike Taylor <[email protected]> wrote:
> LGTM2 (and thank you for the great explainer). > On 3/12/26 6:33 p.m., Philip Jägenstedt wrote: > > LGTM1, this is a clear gap in feature detection, thanks for closing it! > > On Wed, Mar 11, 2026 at 10:18 PM 'Kevin Babbitt' via blink-dev < > [email protected]> wrote: > >> *Note: *This feature is a bit unusual in that it was implemented behind >> a flag but not advertised on blink-dev with an I2P or dev trial >> announcement. I picked it up after initial implementation, got clarity on >> some open spec issues, and adjusted the implementation to match CSSWG >> resolutions. >> >> *Contact emails* >> [email protected] >> >> *Explainer* >> >> https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/AtRuleFeatureDetection/explainer.md >> >> *Specification* >> https://drafts.csswg.org/css-conditional-5/#support-definition-at-rules >> >> *Summary* >> This feature adds an `at-rule()` function to CSS `@supports` which >> enables authors to feature-detect support for CSS at-rules. >> >> *Blink component* >> Blink>CSS >> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> >> >> *Web Feature ID* >> supports-at-rule <https://webstatus.dev/features/supports-at-rule> >> >> *Motivation* >> Feature detection is a W3C TAG design principle and a tool that Web >> authors rely on for graceful degradation of their pages. Currently, the >> only way for web developers to detect support for CSS at-rules is to use >> JavaScript. This feature allows at-rule support to be detected using the >> same `@supports` feature used to detect support for CSS properties. >> >> *Initial public proposal* >> https://github.com/w3c/csswg-drafts/issues/2463 >> >> *TAG review* >> https://github.com/w3ctag/design-reviews/issues/1176 >> >> *TAG review status* >> Issues addressed >> >> *Goals for experimentation* >> None >> >> *Risks* >> >> >> *Interoperability and Compatibility* >> Minimal risks; this feature is purely additive. >> >> *Gecko*: No signal ( >> https://github.com/mozilla/standards-positions/issues/1310) >> >> *WebKit*: No signal ( >> https://github.com/WebKit/standards-positions/issues/565) >> >> *Web developers*: Positive There have been several requests for this >> feature; some examples: https://github.com/w3c/csswg-drafts/issues/9743 >> https://ruhr.social/@nilsbinder/112721678680237204 >> https://mastodon.social/@xro/113106213499516093 >> https://bsky.app/profile/badrihippo.fosstodon.org.ap.brid.gy/post/3m6vupwqhbkk2 >> >> *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?* >> N/A >> >> >> *Debuggability* >> Exposure in Dev Tools is the same as for existing `@supports` rules. >> >> *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-conditional/js/supports-at-rule.html?label=experimental&label=master&aligned >> >> *Flag name on about://flags* >> enable-experimental-web-platform-features >> >> *Finch feature name* >> CSSSupportsAtRuleFunction >> >> *Rollout plan* >> Will ship enabled for all users >> >> *Requires code in //chrome?* >> False >> >> *Tracking bug* >> https://issues.chromium.org/issues/40211832 >> >> *Estimated milestones* >> Shipping on desktop >> 148 >> DevTrial on desktop >> 143 >> Shipping on Android >> 148 >> DevTrial on Android >> 143 >> Shipping on WebView >> 148 >> >> >> *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 known open issues on `@supports at-rule()` itself. There were some >> expansions to the feature discussed to test for certain descriptors or >> context, but the CSSWG resolved to separate these more detailed queries out >> to a separate feature `@supports-condition`; see discussion at >> https://github.com/w3c/csswg-drafts/issues/12622. >> >> *Link to entry on the Chrome Platform Status* >> https://chromestatus.com/feature/5110744177836032?gate=4696535686316032 >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com/>. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CH4PR00MB2495314F25A2D84629348CC0C047A%40CH4PR00MB2495.namprd00.prod.outlook.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CH4PR00MB2495314F25A2D84629348CC0C047A%40CH4PR00MB2495.namprd00.prod.outlook.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAARdPYffhV1zUrz8msNPTO-ZN1gVjTRkbfrx%3DW-7pFVMneh%3DPA%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAARdPYffhV1zUrz8msNPTO-ZN1gVjTRkbfrx%3DW-7pFVMneh%3DPA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/336c5956-27f2-4db6-ac44-c475f953f920%40chromium.org > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/336c5956-27f2-4db6-ac44-c475f953f920%40chromium.org?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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