Thank you for the review! And yes, the relevant tests in https://wpt.fyi/results/css/css-align are all passing (the tests which formerly used `flex-start/end`).
Best, Celeste ________________________________ From: Philip Jägenstedt <[email protected]> Sent: Thursday, October 15, 2026 2:10 AM To: Celeste Pan <[email protected]> Cc: [email protected] <[email protected]>; Alison Maher <[email protected]>; Hoch Hochkeppel (HE/HIM) <[email protected]>; Yanling Wang <[email protected]> Subject: Re: [blink-dev] Intent to Ship: CSS flow-start and flow-end alignment keywords You don't often get email from [email protected]. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> https://wpt.fyi/results/css/css-align is a larger test suite, are all of the relevant tests already passing? (I tried to dig in but https://github.com/web-platform-tests/wpt.fyi/issues/5203 got in the way of filtering.) And thanks for filing https://github.com/web-platform-dx/web-features/issues/4282! On Wed, Oct 14, 2026 at 8:04 PM 'Celeste Pan' via blink-dev <[email protected]<mailto:[email protected]>> wrote: Contact emails [email protected]<mailto:[email protected]>, [email protected]<mailto:[email protected]>, [email protected]<mailto:[email protected]>, [email protected]<mailto:[email protected]> Explainer No information provided Specification https://github.com/w3c/csswg-drafts/pull/14539 Summary It was resolved in the CSSWG that we should introduce the flow-start/end keywords as value aliases for the existing flex-start/end keywords. These are needed for alignment in the case of placement reversals. flow-start in CSS Grid-Lanes would indicate the starting edge of the container at which placement begins, which is useful in the case where placement is reversed (`fill-reverse`, `track-reverse`, discussed in this CSSWG issue: [css-grid-3][masonry] item-flow row vs. column in masonry layouts · Issue #12803 · w3c/csswg-drafts). Because these are acting as value aliases, we expect flex-start/end to follow the logical directions in Grid Lanes, as well, which will expand the definition of these keywords from only applying special behavior in flexbox to applying to any layout mode whose logical start/end is different from its physical start/end. For serialization, if either flex-start/end or flow-start/end is used, the returned serialized value should be flow-start/end. Blink component Blink>CSS<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> Web Feature ID https://github.com/web-platform-dx/web-features/issues/4282<https://webstatus.dev/features/https://github.com/web-platform-dx/web-features/issues/4282> Motivation In grid-lanes, there is currently no alignment keyword to allow us to align based on the start of content placement when reversal is present; instead, we can only currently use the logical container start/end. We wanted a keyword that behaves the way flex-start/end does in flexbox containers. Introducing flow-start/end allows us to align based on content placement start/end, and aliasing it to flex-start/end means that we can have the same keyword used across flexbox, grid, and grid-lanes layout with the same expected behavior. Initial public proposal https://github.com/w3c/csswg-drafts/issues/12803 TAG review N/A - the feature is an alias to an existing API and documentation of its resolution can be found in this CSSWG issue: <https://github.com/w3c/csswg-drafts/issues/12803> https://github.com/w3c/csswg-drafts/issues/12803 TAG review status N/A Goals for experimentation None Risks * Interoperability and Compatibility For serialization, if either flex-start/end or flow-start/end is used, the returned serialized value should be flow-start/end. This could introduce compatibility concerns for sites that rely on the existing serialization of flex-start/end. Because of this, we plan to use a second flag to introduce a separate gate for the new serialization behavior of flex-start/end so that if we receive reports of site breakages as a result, we can disable the serialization behavior separately from the new keywords. Gecko: Positive (https://github.com/mozilla/standards-positions/issues/1455#issuecomment-5839398061) WebKit: No Signal (https://github.com/WebKit/standards-positions/issues/723) Web developers: No Signal (While we don't have direct signals from developers on flow-start/end, flex-start/end are used by a number of sites to achieve alignment based on placement direction, thus, because grid lanes also supports reversals, a more generic keyword allows us to extend the behavior to other layout modes to achieve the same use cases that developers are able to achieve in flexbox today) Other signals: * WebView application risks: N/A Debuggability They will have same debugging capabilities as flex-start/end. 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 <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> web-platform-tests<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>? Yes https://wpt.fyi/results/css/css-align?label=master&label=experimental&aligned&q=css-align Flag name on about://flags No information provided Finch feature name CSSFlowStartAndEnd,CSSFlowStartAndEndSerialization Rollout plan Will ship enabled for all users Requires code in //chrome? False Tracking bug https://issues.chromium.org/issues/555299635 Estimated milestones Dev Trial 157 Shipping 158 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/5069051687731200?gate=5575518593351680 Links to previous Intent discussions Intent to Prototype: <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/DM4PR00MB24735CF983FF2BE273586298D3B52%40DM4PR00MB2473.namprd00.prod.outlook.com> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/DM4PR00MB24735CF983FF2BE273586298D3B52%40DM4PR00MB2473.namprd00.prod.outlook.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]<mailto:[email protected]>. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/BL4PR00MB24712DB30828C8E0EA0FCD1BD39D2%40BL4PR00MB2471.namprd00.prod.outlook.com<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/BL4PR00MB24712DB30828C8E0EA0FCD1BD39D2%40BL4PR00MB2471.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/BL4PR00MB2471708FEB5C5D513A07D21AD39C2%40BL4PR00MB2471.namprd00.prod.outlook.com.
