LGTM1 On Thursday, October 15, 2026 at 11:22:04 AM UTC-7 Celeste Pan wrote:
> 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]> wrote: > > Contact emails > [email protected], [email protected], [email protected], > [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]. > 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/98e24619-7fcd-4c6d-bf68-2f3dc2274e89n%40chromium.org.
