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Updates for Firefox 149 beta#29135

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Elchi3 merged 1 commit intomdn:mainfrom
Elchi3:firefox-149-beta
Feb 26, 2026
Merged

Updates for Firefox 149 beta#29135
Elchi3 merged 1 commit intomdn:mainfrom
Elchi3:firefox-149-beta

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@Elchi3 Elchi3 commented Feb 26, 2026

The https://collector.openwebdocs.org/ project (v10.17.4) found new features shipping in Firefox 149 beta which was released yesterday. Currently, the collector covers about 90% of BCD, so the following list might not be exhaustive. Also, if a feature is in Firefox Nightly only, it is not considered here.

With this PR, BCD considers the following 36 features as shipping in Firefox 149:

  • api.CloseWatcher
  • api.CloseWatcher.CloseWatcher
  • api.CloseWatcher.cancel_event
  • api.CloseWatcher.close
  • api.CloseWatcher.close_event
  • api.CloseWatcher.destroy
  • api.CloseWatcher.requestClose
  • api.HTMLInputElement.colorSpace
  • api.HTMLMediaElement.captureStream
  • api.PopStateEvent.hasUAVisualTransition
  • api.ReportingObserver
  • api.ReportingObserver.ReportingObserver
  • api.ReportingObserver.worker_support
  • api.ReportingObserver.disconnect
  • api.ReportingObserver.observe
  • api.ReportingObserver.takeRecords
  • api.ShadowRoot.referenceTarget
  • api.createImageBitmap.options_resizeQuality_parameter
  • css.properties.alignment-baseline
  • css.properties.alignment-baseline.baseline
  • css.properties.alignment-baseline.middle
  • css.properties.alignment-baseline.text-bottom
  • css.properties.alignment-baseline.text-top
  • css.properties.baseline-shift
  • css.properties.baseline-shift.bottom
  • css.properties.baseline-shift.center
  • css.properties.baseline-shift.sub
  • css.properties.baseline-shift.super
  • css.properties.baseline-shift.top
  • css.properties.dominant-baseline.text-bottom
  • css.properties.dominant-baseline.text-top
  • css.properties.vertical-align.center
  • css.properties.vertical-align.first
  • css.properties.vertical-align.last
  • html.elements.template.shadowrootreferencetarget (added in a different PR)
  • webdriver.bidi.browser.setDownloadBehavior (added in a different PR)

See also mdn/mdn#810 and https://www.mozilla.org/en-US/firefox/149.0beta/releasenotes/

cc @pepelsbey

@github-actions github-actions bot added data:api Compat data for Web APIs. https://developer.mozilla.org/docs/Web/API data:css Compat data for CSS features. https://developer.mozilla.org/docs/Web/CSS size:l [PR only] 101-1000 LoC changed labels Feb 26, 2026
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Tip: Review these changes grouped by change (recommended for most PRs), or grouped by feature (for large PRs).

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Looks good! Thank you 🙂

@Elchi3 Elchi3 merged commit 14909b3 into mdn:main Feb 26, 2026
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@Elchi3 Elchi3 deleted the firefox-149-beta branch February 26, 2026 16:50
@mdn-bot mdn-bot mentioned this pull request Feb 26, 2026
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data:api Compat data for Web APIs. https://developer.mozilla.org/docs/Web/API data:css Compat data for CSS features. https://developer.mozilla.org/docs/Web/CSS size:l [PR only] 101-1000 LoC changed

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