Release Notes for Safari Technology Preview 53

Safari Technology Preview Release 53 is now available for download for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions 229535-230029.

This release of Safari Technology Preview has a known issue where the modal won’t appear for websites that prompt for camera or microphone access.

Service Workers

  • Changed to use one service worker process per security origin (r229735)
  • Changed to use the same SWServer for all ephemeral sessions (r229872)
  • Fixed promptly terminating service worker processes when they are no longer needed (r229927)
  • Included the security origin in the service worker process name (r229878)


  • Added support for VCP encoder on macOS and iOS (r229920)
  • Fixed the RTCPeerConnection constructor to throw an exception for bad configuration parameters (r229645)
  • Fixed setting SenderTrack to null calling removeTrack with RTCRtpSender (r229587)


  • Fixed CSS mask images to be retrieved using potentially CORS-enabled fetch (r230006)
  • Fixed loading the stylesheet when changing the <link> element rel attribute from preload to stylesheet (r229585)


  • Fixed invalidating descendants for :nth-child and :nth-of-type pseudo classes only when needed (r229537)
  • Fixed positioning for text with letter spacing (r229867)


  • Added Fullscreen API as an Experimental Feature (r229680)
  • Prevented SVG root from being skipped while marking percentage height descendants dirty (r229849)


  • Fixed table row count when role="row" is added to in DOM (r229879)


  • Fixed CSS Grid auto repeat tracks computation with definite min sizes (r229897)


  • Added a query and fragment exception to the History API’s unique origin restriction (r229540)

Web Inspector

  • Changed “Force Print Media Styles” to not persist across Web Inspector sessions (r229686)
  • Changed to not show checkboxes for invalid properties in the Styles sidebar (r229941)
  • Fixed the ability to add a new class by editing the class attribute in the DOM tree outline (r229744)
  • Fixed an instance of the main WebGL canvas having no reported size in the Canvas Tab (r229659)
  • Fixed a recording initiated by the user to properly show immediately on completion (r229620)
  • Fixed session dividers not being added when Console tab is not visible (r229785)
  • Fixed flashing when switching between nodes in the Styles sidebar (r229922)
  • Fixed losing focus when editing a property while a page is being loaded (r229787)
  • Prevented the Shift-Command-Left Arrow (⇧⌘←) and Shift-Command-Right Arrow (⇧⌘→) keys from switching tabs when focused on color picker text fields (r230001)
  • Removed redundant tooltips (r229543)