My thought is that, because Firefox doesn't ship anchor-valid yet, it seems helpful to just file the positions request to encourage interop on this subfeature. Especially since this feature came a bit later than the others due to additional spec discussion to align on its semantics, so perhaps it fell through the cracks a bit (like it did in Chromium until just now).
On Fri, Sep 25, 2026 at 9:30 AM Mason Freed <[email protected]> wrote: > > On Thu, Sep 24, 2026 at 5:07 PM Chris Harrelson <[email protected]> > wrote: > >> Could you file a Mozilla standards request? >> > > So there's already a (positive) standards position for anchor positioning > as a whole: https://github.com/mozilla/standards-positions/issues/794. Do > you think `anchor-valid` by itself deserves its own standards position? I > think perhaps we should think about #794 as a position on the entire > feature, including all sub-features. If you disagree, of course I'm happy > to file a new one. > > Thanks, > Mason > > > >> On Wed, Sep 23, 2026 at 3:56 PM Mason Freed <[email protected]> wrote: >> >>> *Contact emails* >>> [email protected] >>> >>> *Explainer* >>> *No information provided* >>> >>> *Specification* >>> https://drafts.csswg.org/css-anchor-position-1/#position-visibility >>> >>> *Summary* >>> The `anchors-valid` value was implemented as part of >>> https://crbug.com/329703412 but subsequently reverted, due to spec >>> questions about the exact definition of the value. Since that time, the >>> value has been renamed to `anchor-valid` (see >>> https://chromestatus.com/feature/5136123851571200) and also better >>> defined to be clear that only the default anchor matters, resolving a lot >>> of ambiguity, and making this value shippable. >>> >>> *Blink component* >>> Blink>CSS >>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ECSS%22> >>> >>> *Web Feature ID* >>> anchor-positioning <https://webstatus.dev/features/anchor-positioning> >>> >>> *Motivation* >>> *No information provided* >>> >>> *Initial public proposal* >>> *No information provided* >>> >>> *Search tags* >>> position-visibility >>> <https://chromestatus.com/features#tags:position-visibility>, >>> anchor-valid <https://chromestatus.com/features#tags:anchor-valid>, >>> anchors-valid <https://chromestatus.com/features#tags:anchors-valid> >>> >>> *TAG review* >>> *No information provided* >>> >>> *TAG review status* >>> Not applicable >>> >>> *Goals for experimentation* >>> None >>> >>> *Risks* >>> >>> >>> *Interoperability and Compatibility* >>> This is new support for a value for `position-visibility` so it should >>> not create compat risks. Shipping this value will improve interop - WebKit >>> already ships it. >>> >>> *Gecko*: No signal >>> >>> *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 information provided* >>> >>> *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-anchor-position?label=master&label=experimental&aligned&q=position-visibility >>> >>> *Flag name on about://flags* >>> *No information provided* >>> >>> *Finch feature name* >>> CSSPositionVisibilityAnchorValid >>> >>> *Rollout plan* >>> Will ship enabled for all users >>> >>> *Requires code in //chrome?* >>> False >>> >>> *Tracking bug* >>> https://crbug.com/333421963 >>> >>> *Estimated milestones* >>> Shipping on desktop 157 >>> DevTrial on desktop 157 >>> Shipping on Android 157 >>> DevTrial on Android 157 >>> Shipping on WebView 123 >>> >>> *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/5136856479039488?gate=5692419038380032 >>> >>> 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/CAM%3DNeDgQ_W7-2FxYgaXc4-r7-vuaq1rexfHn4w4YEEW-Cz0%2BSA%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDgQ_W7-2FxYgaXc4-r7-vuaq1rexfHn4w4YEEW-Cz0%2BSA%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/CAM%3DNeDjXTYLG_kz2nEhK19VGFOvQQZcds38-6jzoDk7ZeNBUQg%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM%3DNeDjXTYLG_kz2nEhK19VGFOvQQZcds38-6jzoDk7ZeNBUQg%40mail.gmail.com?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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