Release Notes for Safari Technology Preview 157

Safari Technology Preview Release 157 is now available for download for macOS Monterey 12.3 or later and macOS Ventura. 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: 255077@main…255891@main

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 event breakpoints to be case-insensitive and regular expression matching (255196@main)
    • Fixed disabling inline breakpoints unexpectedly removing them (255292@main)
    • Fixed inline breakpoints appearing for minified resources before they are pretty-printed (255200@main)


  • Added support for font-synthesis longhand properties (255171@main)
  • Added support for last baseline alignment for CSS Grid (255455@main)
  • Added support for last baseline alignment for Flexbox containers (255383@main)
  • Added support for lh and rlh units (255540@main)
  • Added margin when computing the baseline position for tables (255357@main)
  • Changed outline to follow border-radius (255314@main, 255300@main)
  • Changed to treat rem and rlh as absolute units for font size (255594@main)
  • Changed to allow the font-variant-east-asian shorthand property in any position (255134@main)
  • Changed to only preserve a scroll snap target if there are targets for both axes (255493@main)
  • Changed CSS Keyframe name handling to not allow CSS-wide keywords (255640@main)
  • Changed to use min-intrinsic size to compute min-content size for non-replaced flex items (255858@main)
  • Fixed the display property value of a computed style to be "none" instead of "inline" for an <audio> element without controls (255528@main)
  • Fixed font-style: oblique to allow angles equal to 90deg or -90deg (255875@main)
  • Fixed font-weight to be clamped to 1 as a minimum (255873@main)
  • Fixed the left-aligned contentEditable caret instead of centered when the :before pseudo-element is used (255333@main)
  • Fixed CSS 3D transform by matrix3d() with translations to take page zoom into account (255416@main)
  • Unprefixed font-size: -webkit-xxx-large (255602@main)
  • Updated @font-palette-values override-colors order (255604@main)


  • Fixed flickering while scrolling when the keyboard scrolling spring damping animation doesn’t finish (255306@main, 255099@main)


  • Added support for class static initialization blocks (255173@main)
  • Changed the default style of Intl.DurationFormat from “digital” to “short” (255255@main)
  • Fixed Intl.NumberFormat ignoring maximumFractionDigits with compact notation for currency and decimal (255691@main)
  • Improved Object.entries runtime function performance (255470@main)
  • Updated useGrouping handling for Intl.NumberFormat (255275@main)


  • Added support for WebCodecs encoder bitrate related parameters (255476@main)
  • Added support for WebCodecs video encoder flush (255785@main)
  • Added support for WebCodecs Validate VideoFrameInit algorithm (255786@main)
  • Added support for WebCodecs VideoFrame allocationSize (255313@main)
  • Added support for WebCodecsVideoEncoder (255316@main, 255262@main)
  • Added support for WebCodecsVideoDecoder (255215@main, 255138@main)
  • Added support for WebCodecs VideoFrame copyTo (255429@main)
  • Added support for WebCodecsVideoDecoder with VPx backend (255138@main)
  • Added support for AVC H.264 WebCodecsVideoEncoder and WebCodecsVideoDecoder (255430@main, 255422@main)
  • Added support for GPU-based WebCodecsVideoDecoder flush (255388@main)
  • Added cropping support to WebCodecsVideoFrame copyTo (255716@main)
  • Added initial implementation to VideoFrame (255259@main)
  • Added support for RGBX and BGRX pixel formats (255390@main)
  • Added WebCodecs VideoFrame support for createImageBitmap (255776@main)
  • Ensured VPx WebCodecs encoders and decoders are created asynchronously (255478@main)
  • Ensured the bitrate and framerate are set for VPx encoders (255666@main)
  • Fixed canvas to be able to draw a WebCodecsVideoFrame (255720@main)
  • Validated width, height, x and y for I420 and NV12 video frames (255489@main)


  • Added support for CSSNumericValue.toSum() (255679@main)
  • Added support for CSSNumericValue.parse() (255791@main)
  • Added support for CSSTransformValue.toMatrix (255299@main)
  • Added support for EXT_provoking_vertex draft extension (255261@main)
  • Added support for the Sec-Fetch-Site header (255810@main)
  • Added support for cancel event support on <input type=file> (255394@main)
  • Added support for referrerpolicy in link headers (255354@main)
  • Added a log channel for IntersectionObserver (255197@main)
  • Added the class FilterTargetSwitcher (255802@main)
  • Changed to fire an error event when CSP blocks inline stylesheets (255744@main)
  • Changed to fire an error event when link preload fails synchronously (255740@main)
  • Fixed CSSPerspective.toMatrix() to throw an exception if its length is not compatible with a px unit (255876@main)
  • Fixed CSSTransformComponent.toMatrix() to flatten to two-dimenions if necessary (255290@main)
  • Fixed headers iteration to not happen on the cached headers list (255639@main)
  • Made onpointerlockchange and onpointerlockerror enumerable (255153@main)
  • Updated ResizeObserver and IntersectionObserver timing to match other browsers (255132@main)


  • Accept image/jpg for compatibility (255268@main)
  • Changed to enforce Low Power Mode and Optimize Video Streaming setting by tone mapping HDR video to SDR (255127@main)
  • Changed sizing of video element to use width and height HTML attributes to calculate a natural aspect ratio before the video file loads (255743@main)
  • Changed to switch to an alternate <source> element for AirPlay when necessary (255624@main)
  • Fixed the display able to go to sleep when the camera is on (255636@main)

Web Animations

  • Fixed Animation.commitStyles() triggering a mutation even when the styles are unchanged (255129@main)
  • Fixed updating timing to invalidate the effect (255863@main)
  • Updated to account for iterationComposite when blending (255834@main)


  • Added the display of a thumbnail of selected file for <input type=file> on macOS (255355@main)


  • Fixed accessibility for the <meter> and <progress> elements when -webkit-appearance: none or appearance: none is set (255836@main)
  • Fixed accessibility to not limit navigation when focus is explicitly moved outside of a modal (255665@main)
  • Fixed a bug causing VoiceOver to double-read list markers and not output braille for list items (255276@main)


  • Fixed Cross-Origin-Embedder-Policy incorrectly blocking scripts on a cache hit (255302@main)


  • Capped cookie lifetimes to 7 days for responses from third-party IP addresses (255849@main)
  • Omitted document.referrer for third-party requests while in ephemeral mode (255649@main)

Safari Web Extensions

  • Added support for the modifyHeaders action type in Declarative Net Request rules
  • Fixed Declarative Net Request rules not loading after an extension was turned off and then back on