Release Notes for Safari Technology Preview 124

Safari Technology Preview Release 124 is now available for download for macOS Big Sur and macOS Catalina. 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 274641-275811.

Web Inspector

  • Added autocomplete for experimental CSS Color values: hwb, lch, lab, color-mix, color-contrast (r275310)
  • Changed grid overlay track size labels to show implicit auto value and no computed size (r275559)
  • Fixed grid layout labels that were getting drawn outside the viewport (r275128)
  • Fixed CSS Grid overlay track sizes when inline styles are applied to the element (r275293)
  • Fixed a bug with more than two timeline recordings not showing a timescale (r275337)
  • Fixed grid overlay areas appearing offset from their actual areas when the grid container has a border set (r275529)
  • Fixed grid overlay to honor writing modes and RTL layout direction. (r275519)
  • Fixed grid overlay line numbers showing implicit tracks with negative line numbers (r275558)
  • Improved grid overlay label appearance (r275560)
  • Removed the duplicate Box Model section from Layout panel in Elements Tab (r275545)


  • Accounted for cover and contain when interpolating background-size (r275202)
  • Accounted for hanging and each-line when blending text-interpolation (r275224)
  • Added support for animating the vertical-align CSS property (r275160)
  • Animated pseudo element style resolved against wrong parent style (r275277)
  • Fixed interpolation of the caret-color CSS property (r275092)
  • Computed style for a border-radius corner should never be 0px when the provided width isn’t 0px (r275273)
  • Enabled hanging and each-line keywords for the text-indent CSS property (r275199)
  • Fixed align-content issues in Flexbox (r275416)
  • Fixed max-height percentages getting wrongly resolved for replaced grid items in nested percentage flexboxes (r275758)
  • Fixed min and max widths of grid affected by ancestor (r275754)
  • Fixed initial horizontal scrollbar position when vertical scrollbar is on the left (r275811)
  • Fixed max-content on tables with percentage cell widths (r275462)
  • Improved interpolation of the shape-outside CSS property (r275015)
  • Prevented negative heights in CSS Grid (r274933)
  • Supported animation of the tab-size CSS property (r274939)
  • Updated CSS Color 5 color-mix() implementation to match the latest draft spec (r274947)


  • Fixed Intl.Locale to not assume is8Bit (r274784)
  • Fixed Object.freeze(this) at the global scope to not lose a reference to a WatchpointSet (r274882)
  • Fixed RegExp interpreter not to match against non-BMP characters with multiple dots (r274806, r274945)
  • Fixed incorrect Array toString() if join() is not callable (r275544)


  • Enabled the ability to prevent scrolling in Element.focus() (r274812)
  • Implemented AbortSignal.abort() (r274773)
  • Propagated user gestures through requestAnimationFrame just like setTimeout (r275187)
  • ServiceWorker should save module scripts (r275751)


  • Fixed aspect-ratio to recompute on hover (r275377)
  • Implemented text rendering on OffscreenCanvas in a Worker (r275420)

Wheel Events

  • Allowed wheel events to trigger high frequency DisplayLinks (r275440)

Web Driver

  • Fixed SendKeys on <input type="file"> returning element not found in some cases (r275050)


  • Enabled Metal ANGLE backend for WebGL (r274927)


  • Implemented RTCDataChannel transfer (r274758)


  • Fixed WebCrypto to support AES-GCM 0 byte encryption (r275535)


  • Fixed scrolling momentum with scroll-snap-type: x mandatory when the scroller scrolls vertically (r274853)
  • Fixed scroll-snap-stop: always not respected during momentum scrolling (r274726)

Web Extensions

  • Allow wss:// URL in content_security_policy to allow extension pages to use WebSocket connections