LGTM3
/Daniel
On 2026-10-21 19:15, Chris Harrelson wrote:
Excellent!
LGTM2
On Wed, Oct 21, 2026 at 10:14 AM 'Celeste Pan' via blink-dev
<[email protected]> wrote:
Hi Chris,
Thank you for the review! The spec PR actually just landed:
[css-align-3][css-grid-3] Define flow-start/end alignment aliases
(#14052) by celestepan · Pull Req…
<https://github.com/w3c/csswg-drafts/pull/14539>!
Best,
Celeste
------------------------------------------------------------------------
*From:* Chris Harrelson <[email protected]>
*Sent:* Wednesday, October 21, 2026 8:12 AM
*To:* Daniel Clark <[email protected]>
*Cc:* blink-dev <[email protected]>; [email protected]
<[email protected]>; Celeste Pan
<[email protected]>; Alison Maher <[email protected]>;
Hoch Hochkeppel (HE/HIM) <[email protected]>; Yanling Wang
<[email protected]>; Philip Jägenstedt <[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
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I'd like to wait for the spec PR to land; it's currently under review.
On Mon, Oct 19, 2026 at 11:28 AM 'Dan Clark' via blink-dev
<[email protected]> wrote:
Can you please request the other reviews (or request N/A) in
Chromestatus (Enterprise, Testing, Adoption)?
On Monday, October 19, 2026 at 11:26:36 AM UTC-7
[email protected] wrote:
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
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Learn why this is important
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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
<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
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