Release Notes for Safari Technology Preview 110

Safari Technology Preview Release 110 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 263214-263988.


  • Added a functional WebRTC VP9 codec (r263734, r263820)
  • Allowed registering VP9 as a VT decoder (r263894)
  • Added support for freeze and pause receiver stats (r263351)
  • Added MediaRecorder.onstart support (r263671, r263896)
  • Changed MediaRecorder to support peer connection remote video tracks (r263928)
  • Enabled VTB required low latency code path (r263931)
  • Fixed MediaRecorder stopRecorder() returning an empty Blob after first use (r263511, r263633, r263891)
  • Fixed MediaRecorder.start() Method ignoring the timeslice parameter (r263565, r263651, r263892)
  • Fixed RTCDataChannel.bufferedAmount to stay the same even if channel is closed (r263655)
  • Updated the max width and height for mock sources (r263844)

Web Authentication

  • Improved UI for PIN entry for security keys

Web Animations

  • Keyframe animation with infinite iteration count doesn’t show up in the Animations timeline (r263400)


  • Changed to require a <form> to be connected before it can be submitted (r263624)
  • Fixed window.location.replace with invalid URLs to throw (r263647)
  • Fixed the behavior when setting"??" (two question marks) (r263637)
  • Changed to allow selecting HEIF images if the ‘accept’ attribute includes an image MIME type that the platform can transcode (r263949)
  • Added referrerpolicy attribute support for <link> (r263356, r263442)
  • Allow setting empty host/hostname on URLs if they use file scheme (r263971)
  • Allow the async clipboard API to write data when copying via menu action or key binding (r263480)


  • Changed to check for mode=“showing” to consider a text track as selected in the tracks panel (r263802)


  • Changed to allow indefinite size flex items to be definite with respect to resolving percentages inside them (r263399)
  • Changed to not include scrollbar extents when computing sizes for percentage resolution (r263794)
  • Fixed pointer events (click/hover/etc) passing through flex items, if they have negative margin (r263659)


  • Changed to resolve viewport units against the preferred content size (r263311)


  • Fixed overlapping content when margin-right is present (r263550)
  • Fixed content sometimes missing in nested scrollers with border-radius (r263578)


  • Fixed honoring aria-modal nodes wrapped in aria-hidden (r263673)
  • Implemented relevant simulated key presses for custom ARIA widgets for increment and decrement (r263823)

Bug Fixes

  • Fixed the indeterminate progress bar animation periodically jumping in macOS Big Sur (r263952)


  • Enabled RelativeTimeFormat and Locale by default (r263227)
  • Configured option-offered numberingSystem in Intl.NumberFormat through locale (r263837)
  • Changed Intl.Collator to set usage:”search” option through ICU locale (r263833)
  • Fixed Promise built-in functions to be anonymous non-constructors (r263222)
  • Fixed incorrect TypedArray.prototype.set with primitives (r263216)

Storage Access API

  • Added the capability to call the Storage Access API as a quirk, on behalf of websites that should be doing it themselves (r263383)

Text Manipulation

  • Updated text manipulation to exclude text rendered using icon-only fonts (r263527)
  • Added a new text manipulation heuristic to decide paragraph boundary (r263958)


  • Enabled referrer policy attribute support by default (r263274)
  • Changed image crossorigin mutations to be considered “relevant mutations” (r263345, r263350)

Web Inspector

  • Added a tooltip to the icon of resources replaced by a local override explaining what happened (r263429)
  • Allow selecting text of Response (DOM Tree) in Network tab (r263872)
  • Adjusted the height of title area when Web Inspector is undocked to match macOS Big Sur (r263377, r263402)