Release Notes for Safari Technology Preview 149

Safari Technology Preview Release 149 is available for macOS Monterey 12.3 or later and for macOS Ventura beta. Updates to Safari Technology Preview are no longer available for macOS Big Sur. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS Monterey, or System Settings under General → Software Update on macOS Ventura.

This release includes WebKit changes between: 251460.7@safari-7614.1.17-branch…251769.19@safari-7614.1.19.1-branch

Note: Shared Tab Groups and syncing for Tab Groups, Website Settings, and Web Extensions are not enabled in this release.

Web Inspector

  • Elements Tab
    • Added support for forcing pseudo-class :focus-visible, :focus-within, and :target (251656@main, 251628@main)
    • Fixed empty space in the filter bar for the Fonts details sidebar (251704@main)
  • Extensions
    • Fixed Web Inspector window becoming inactive when an extension tab is selected (251645@main)


  • Added support for AVIF images on macOS Ventura and iOS 16 (251850@main)
  • Added support for emitting a resize event from PiP window (251512@main)
  • Fixed a black screen appearing in a muted video element outside the viewport (251596@main)
  • Fixed autoplay for an HTMLMediaElement created while page is interrupted (251691@main)
  • Fixed autoplay when moving a media element from one document to another (251595@main)
  • Fixed WebM to handle a case where a single video frame is appended (251485@main)
  • Fixed video.currentSrc to not get reset when a new load error occurs (251654@main)


  • Implemented the text-align-last property (251540@main)
  • Fixed styling of th elements when explicitly specifying text-align: inherit (251630@main)

CSS Container Queries


  • Fixed repainting rect not taking into account text-underline-offset (251477@main)
  • Fixed incorrect sizing of elements with visually hidden text inside (251483@main)


  • Fixed Temporal regulateTime’s constraints for milliseconds, microseconds, and nanoseconds (behind --useTemporal flag) (251556@main, 251698@main)
  • Fixed Temporal.Instant#round to treat the Big Bang (not the Unix epoch) as zero (behind --useTemporal flag) (251556@main)
  • Fixed Temporal.PlainTime#since to handle ceil and floor properly (behind --useTemporal flag) (251556@main, 251555@main)

Screen Sharing

  • Fixed resuming screen sharing after it is paused (251618@main)

Web Animations

  • Added support for custom properties in @keyframes rules (251733@main)
  • Invalidated animation keyframes using container units on when container size changes (251574@main)


  • Fixed CTAP2_ERR_USER_ACTION_TIMEOUT handling (251511@main)
  • Renamed “cable” transport to “hybrid” (251621@main)
  • Fixed upgrading a legacy platform credential to a passkey does not delete the legacy credential (251646@main)

Navigation Preload

  • Changed to not route the navigation preload response body to the service worker if it can be avoided (251493@main)


  • Added support for waiting for event in custom element (251718@main)
  • Fixed scheduling or firing an event when selection changes for select() and setRangeText() (251716@main)
  • Implemented PerformanceResourceTiming.workerStart in ServiceWorkers (251523@main)
  • Switched Web Share Permissions Policy to * (251487@main)


  • Fixed CORS checks to not unblock cookies (251478@main)