Release Notes for Safari Technology Preview 123

Note: The original end revision for this release was incorrect. These release notes have been updated for the set of changes included in the corrected revision range.

Safari Technology Preview Release 123 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 273903-274641.

Web Inspector

  • Elements Tab
    • Enabled CSS grid badges by default (r274575)
    • Made the border color of the grid badge match to the corresponding outline (r273992)
    • Styles details sidebar panel
      • Fixed pseudo-class checkboxes appearing cramped after resizing window at narrow widths (r274465)
    • Layout details sidebar panel
      • Enabled by default (r274466)
      • Changed to persist user-defined CSS grid overlay colors (r273912)
      • Added button to jump to grid container element (r274157)
      • Added checkbox to toggle all grid overlays (r274268)
      • Improved grid overlay to adjust for element transforms (rotation, scale, etc.) (r274096)
      • Improved grid overlay to adjust for element inside iframes (r274464)
  • Sources Tab
    • Fixed syntax highlighting for JSX files that aren’t indicated as being JSX (r274230)
  • Timelines Tab
    • Fixed trackpad scrolling in timelines (r274091)
  • Storage Tab
    • Changed to use native datetime-local input for changing expires value in cookie popover (r274593)

CSS Aspect Ratio

  • Enabled support for the CSS aspect-ratio property by default (r274424)
  • Added support for aspect-ratio in intrinsic sizing calculations (r274068)
  • Implemented CSS aspect-ratio interpolation (r274415)
  • Treated flexbox min-intrinsic like *-content (r274419)


  • Changed to consider intrinsic sizes as automatic whenever the block axis of the flex item is the flexible box main size (r273955)
  • Fixed orthogonal items with percentage sizes in Flexbox (r273958)
  • Prevented radio buttons used as a flex item from shrinking below its size (r274411)
  • Fixed grid track sizing when using relative sized items in auto column tracks (r274596)
  • Fixed replaced element definiteness as a grid-item (r274099)
  • Fixed position: sticky behavior in a table with dir=RTL (r273982)
  • Fixed :focus-visible to not match the body element after a keyboard event (r274365)
  • Prevented word-wrap and overflow-wrap from overriding hyphens (r274008)

Web Animations

  • Changed border-width, column-width, outline-width, perspective, flex-grow, and flex-shrink to not allow negative values (r274142)
  • Corrected blending for column-width and column-count CSS properties (r274147)
  • Corrected blending of the flex-basis CSS property (r274198)
  • Corrected auto value handling when blending z-index (r274055)
  • Fixed setKeyframes() to preserve the animation’s current offset (r274165)
  • Fixed interpolation of clip CSS property (r274391)
  • Fixed interpolation of orphans and widows CSS properties (r274383)
  • Improved background-size interpolation (r274234)
  • Improved blending of Length and other Length-related types (r274038)
  • Improved font-variation-settings interpolation (r274235)
  • Supported animation of perspective-origin property (r274355)


  • Removed the Origin header if the navigation request goes from POST to GET (r273905)
  • Fixed selecting text via mouse drag in image documents to not trigger click events (r274305)
  • Changed to cancel image loader events after first dispatch (r274357)
  • Prevented dynamic import in service worker (r274404)
  • Increased resource load priority of async scripts from low to medium (r274145)
  • Fixed IndexedDB transactions outdated immediately after it just created (r274269)
  • WebGL APIs are aware of AllowShared (r274438)


  • Implemented Error#cause (r274552)
  • Optimized Boolean constructor calls in DFG and FTL (r274037)
  • Fixed attribute-changing of global variables (r274308)


  • Update wasm ref.func to prepare wasm-function-references proposal (r273962)


  • Added basic (non-momentum) wheel event handling for scroll snap (r274381)


  • Fixed <img> to render RTL text correctly in alt text (r274532)


  • Updated PDF frame conversion (r274377)


  • Fixed video controls staying on screen indefinitely after interacting with the time scrubber (r274293)
  • Fixed MediaRecorder.requestData() not returning all captured media after a pause (r274154)