Release Notes for Safari Technology Preview 144

Safari Technology Preview Release 144 is now available for download for macOS Big Sur and of macOS Monterey. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS.

This release covers WebKit revisions 291506-291957. This release of Safari Technology Preview does not support versions of macOS Monterey prior to 12.3. Please update to macOS Monterey 12.3 or later to continue using Safari Technology Preview.

Note: Tab Groups do not sync in this release.

Web Inspector

  • Fixed page reloading and showing an empty inspector on pages with container queries (r291824)
  • Elements Tab
    • Fixed $0 not being displayed for the selected node after switching to another tab (r291729)
    • Fixed unwanted extra dash when autocompleting CSS variable names in the Styles panel (r291740)
    • Fixed inline swatch popovers not being hidden when the inline swatch is removed (r291628)
  • Console Tab
    • Fixed console.screenshot to no longer have extra transparent pixels at the bottom of viewport screenshots (r291519)


  • Added Typed OM support for container units (r291524)
  • Fixed CSS cascade regarding logical properties (r291546)
  • Fixed incorrect handling of NaN inside calc() for top-level calculation (r291911)
  • Let revert-layer roll back to presentational hints (r291594)
  • Implemented border-image serialization (r291537)
  • Preserved repeat() notation when serializing grid-templates (r291956)
  • Reduce memory usage for large, sparse grids (r291952)
  • Handled finite value with infinite step in round() for calc() (r291841)
  • Fixed incorrect resolution of percentage grid-gaps within subgrids (r291953)

Web Animations

  • Enabled support for mutable timelines by default (r291868)


  • Changed Date.parse to stop returning numbers with fractional part (r291603)
  • Fixed class field initializer with extra parentheses (r291577)


  • Added getAssertion support for virtual HID authenticators (r291624)
  • Specified correct ASCPublicKeyCredentialKind in configureAssertionOptions (r291761)
  • Updated to pass along timeout to ASA and ignore timeout for conditional mediation requests (r291625)


  • Added support for focused and visible ServiceWorkerWindowClient states (r291888)
  • Added a check for whether the origin can access storage in the Storage API (r291726)
  • Disabled custom storage paths for IndexedDB and LocalStorage by default (r291909)
  • Fixed PointerEvent.movementX to not always be 0 (r291886)
  • Fixed Context2D drawImage(img, x, y, w, h) to not throw IndexSizeError when width or height are 0 (r291748)
  • Fixed fetching a Blob URL with an unbounded Range header to correctly generate a Content-Range response header (r291622)
  • Implemented CSSNumericValue.mul, CSSNumericValue.div, CSSNumericValue.add, CSSNumericValue.sub, CSSNumericValue.max, and CSSNumericValue.min (r291597)
  • Implemented ServiceWorkerWindowClient.focus (r291938)


  • Included initial accessibility support for display: contents (r291570)


  • Fixed a bug where clicking anywhere on the progress bar pauses some MSE video implementations (r291629)
  • Fixed video playback for HEVC-encoded video with a lot of b-frames and a wide sliding window (r291813)

Security Policy

  • Fixed website policies not being respected when doing COOP-based process swap (r291606)

Web Extensions

  • Fixed a crash clicking on Safari App Extension toolbar items