Release Notes for Safari Technology Preview 64

Safari Technology Preview Release 64 is now available for download for macOS High Sierra and the beta of macOS Mojave. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab on macOS High Sierra and in the Software Update pane of System Preferences on macOS Mojave. This release covers WebKit revisions 234684-235171.

Custom Elements

  • Fixed the custom element constructor to use HTMLElement in‘s realm (r234957)
  • Fixed custom element to invalidate its style when :defined rule starts to apply (r234953)
  • Changed invoking custom element reactions after constructing and inserting a custom element (r234893)
  • Changed to perform a microtask checkpoint before creating a custom element (r234944)


  • Added the content-length header to the Fetch safe-list (r234840)
  • Disallowed navigations when page cache updates the current document of the frame (r235121)
  • Fixed navigator.sendBeacon to work in pagehide callbacks (r234684)
  • Fixed <object> elements that change from hidden to visible to properly display its content if its URL has a fragment identifier (r234762)


  • Added Experimental Feature support for SourceBuffer.changeType() (r234940)
  • Fixed an issue causing video playback to use more power (r234743)
  • Skipped validation of ideal constraints when selecting matching getUserMedia devices (r234949)


  • Added support for a “name” option for dedicated workers (r235159)
  • Added support for unhandled promise rejections in a Worker (r234846)
  • Changed Date.UTC to not return NaN with only year parameter (r234763)
  • Changed Array.prototype.sort to throw a TypeError if the parameter is a not callable object (r234716)

Storage Access API

  • Changed to use eTLD+1s, not full host names, when granting storage access (r235145)

Web Inspector

  • Added support for breakpoints on arbitrary event names (r234974)
  • Added Initiator information in the Network table (r234963)
  • Allowed breakpoints to be set for specific event listeners (r235103)
  • Allowed recording processing to be stopped midway in the Canvas tab (r235095)
  • Created icons for recordings and shaders in the preview tile of the Canvas tab (r235093)
  • Fixed console.log to prevent firing getters for deep properties (r234780)
  • Fixed the contrast of the error and warning text widget for the source code text editor in Dark Mode (r234736)
  • Fixed XHR content sometimes showing as an error even though the load succeeded (r234702)
  • Fixed ⌘G to work as expected when the find banner is focused (r235147)
  • Provided a default icon for all actions in the Canvas tab (r235141)
  • Prevented tables from centering rows when scrolling them into view (r234882)


  • Changed top not handle prompts that appear while running scripts (r234792)
  • Included all capabilities in the new session response (r234837)
  • Stopped trying to set the caret when focusing a non-text element in the send keys command (r234838)


  • Implemented flow-relative margin, padding, border and sizing properties (r234798)
  • Updated the behavior of percentage row tracks and gutters in CSS Grid (r234687))


  • Fixed WebGL contexts to be updated when the display configuration is changed (r235125)

Bug Fix

  • Fixed color wells to appear pressed when presenting a color picker (r234788)

Safari Push Notifications

  • A user gesture, such as a mouse click, is now required to request the user’s permission to send Safari Push Notifications

Safari Reader