#1175: Other Spec Review: trigger-scope

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Opened Dec 4, 2025

Specification

https://drafts.csswg.org/css-animations-2/#trigger-scope

Explainer

https://github.com/explainers-by-googlers/scroll-triggered-animations/blob/main/TRIGGER_SCOPE.md

Links

  • The WG's request for this TAG review: None <!-- If the WG didn't express consensus to ask the TAG for a review, use the "Other Specification Review" template instead, at https://github.com/w3ctag/design-reviews/issues/new?template=015-other-spec-review.yaml. This is usually a deep link into minutes or an email thread. -->
  • Previous early design review, if any: None
  • An introduction to the feature, aimed at unfamiliar audiences: explainer <!-- Can be the specification's or explainer's introduction, or another section. -->
  • A description of the problems that end-users were facing before this proposal: explainer <!-- See https://w3ctag.github.io/explainer-explainer/#end-user-need -->
  • Alternatives considered: explainer <!-- See https://w3ctag.github.io/explainer-explainer/#alternatives -->
  • Examples of how to use the proposal to solve the end-users' problems: explainer <!-- See https://w3ctag.github.io/explainer-explainer/#describe-proposal -->
  • What do the end-users experience with this proposal: <!-- See https://w3ctag.github.io/explainer-explainer/#describe-proposal -->
  • User research you did to validate the problem and/or design, if any: None
  • Web Platform Tests: In Progress<!-- Or other tests if this is not a web platform feature. -->

The specification

Where and by whom is the work is being done?

  • GitHub repo: None
  • Primary contacts:
    • @DavMila, Google, CSSWG participant
    • @flackr, Google, CSSWG participant
    • @tabatkins, Google, CSSWG participant, spec editor
  • Organization/project driving the specification:
  • This work is being funded by: Google
  • Primary standards group developing this feature: CSSWG
  • Incubation and standards groups that have discussed the design:

Feedback so far

  • Active horizontal reviews: None https:// <!-- Link to an issue like https://github.com/webmachinelearning/webnn/issues/239, https://github.com/WebAssembly/spec/issues/1804, or https://github.com/w3c/did/issues/885, which itself links to the other horizontal reviews. If you haven't started the rest of the horizontal reviews, please consider doing so. -->
  • Multi-stakeholder feedback:
  • Major unresolved issues with or opposition to this specification:
  • Status/issue trackers for implementations: Chrome Status,<!-- Include links to [Mozilla's](https://bugzilla.mozilla.org/), [WebKit's Bugzilla](https://bugs.webkit.org/), and trackers for other implementations if those are known to you. -->

You should also know that...

No response

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Discussions

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Discussed Dec 15, 2025 (See Github)

Lola: Is this a browser request instead of a WG request?

Jeffrey: Yes.

Hadley: Is this still CSS?

Jeffrey: Yes, it’s a refinement. Think it follows a pattern established in other designs.

Lola: I would like to be assigned to this.

Matthew: Can have a look at that as well.

Hadley: Is this a horizontal spec review? Given this is driven by a browser.

Jeffrey: Not really, but it was the most matching review type that was available.

Hadley: Small delta?

Jeffrey: Yes.

Discussed Jan 5, 2026 (See Github)

Jeffrey: I noticed this is still in explainers-by-googlers even though it's merged to the CSS spec, so I'll encourage them to move it.

Discussed Jan 19, 2026 (See Github)

Matthew: It's progressed a bit since I've last looked at it, will look at it this week. Note that it's not an "Other" spec review, it's a full spec review now.

Discussed Jan 26, 2026 (See Github)

Matthew: Checking if this is horizontal review. Linked to scroll-triggered animations (?). Have been looking at the other sections of this spec for APA. Will take up layer.

Discussed Feb 2, 2026 (See Github)

Skipped.

Discussed Feb 9, 2026 (See Github)

Matthew: Need a couple more days.

Discussed Feb 16, 2026 (See Github)

Matthew: from a perspective of consistency, it seems that this is consistent with other parts of CSS. They've also tried to make it all done in the same way. Seems a useful feature, will address some of our concerns about the robustness of the animations when you go back, scroll up, etc. A solution to a genuine problem. Would appreciate another view.

Lola: I will have a look at this.

Discussed Feb 23, 2026 (See Github)

Jeffrey: On the question of Mozilla and Safari support, this was adopted by CSSWG and they're usually paying attention there, so I've been looking at where it was discussed and checking minutes to see who seems interested. My suspicion is they're interested but haven't replied on the standards positions as that's for Chromium's benefit, so think it's likely they are OK with it. Maybe we should change our intake process to allow proponents to point to support from other vendors in any place. Maybe TAG would want to get hold of any evidence of support that may exist.