Release Notes for Safari Technology Preview 24

Safari Technology Preview Release 24 is now available for download for macOS 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 211256-212356.

User Timing

  • Added User Timing as an experimental feature (r211332)
  • Implemented PerformanceObserver for User Timing (r211406)
  • Added support for Performance API (, UserTiming) in Workers (r211594)

Link Preload

  • Added <link preload> as an experimental feature (r211341)
  • Added support for speculative resource loading (r211480)
  • Prevented preloaded resources from being cleared after parsing is done (r211649)
  • Addressed memory issues related to clearing preloaded resources (r211673)


  • Changed Location object to throw a TypeError for Object.preventExtensions() (r211778)
  • Changed Pointer Lock to require keyboard focus (r211652)
  • Changed Pointer Lock events to be delivered directly to the target element (r211650)
  • Changed the HTML Form Validation popover to be dismissed when pressing the Escape key (r211653)
  • Changed the HTML Form Validation popover to respect the minimum font size setting (r212325)
  • Fixed an issue causing Fetch to fail when passing undefined as the headers (r212162)
  • Fixed the <details> element to work correctly when content is changed between closing and opening (r212027)
  • Implemented toJSON() for URL objects (r212193)
  • Improved URL specification compliance (r211636, r212279)
  • Prevented a redundant scroll to top-left corner of the page when navigating back to a URL with no fragment (r212197)
  • Made Symbols configurable when exposed on cross-origin Window or Location objects (r211772)


  • Implemented dynamic import operator (r211280)
  • Changed dynamic import through setTimeout() and setInterval() to correctly inherit SourceOrigin (r211314)
  • Changed scripts load priority to ‘high’ (r211334)
  • Fixed Apple Pay line validation to prevent validating line items that are “pending” (r211446)
  • Implemented ArrayBuffer.prototype.byteLength and SharedArrayBuffer.prototype.byteLength (r212196)
  • Implemented lifting template escape sequence restrictions in tagged templates (r211319)


  • Fixed elements with a backdrop-filter and a mask to correctly mask the backdrop (r211305)
  • Updated line-break:auto to match the latest version of Unicode (r212235)

Web Inspector

  • Enabled the console to evaluate dynamic module import() (r211777)
  • Added CSS color keyword entries for all “grey” and “gray” variations (r211452)
  • Added stroke-linecap property values to CSS autocompletion (r211640)
  • Added a horizontal slider for gradient editor angle value where applicable (r211318)
  • Added a limit on Async Call Stacks for asynchronous loops (r211385)
  • Added a setting to preserve network data on navigation for the Network tab (r211451)
  • Added the ability to show the current value of CSS variables in style rules (r212273)
  • Added a warning that webkitSubtle in WebCrypto is deprecated (r212261)
  • Changed docking Web Inspector to collapse the split console in the Timeline and Network tabs (r211976)
  • Fixed jumping from Search tab results to see the resource in other tabs (Resource, Debugger, Network) (r211608)
  • Fixed a Debugger sidebar panel issue that can cause it to have multiple tree selections (r212171)
  • Fixed DOM tree view collapsing when switching back to the Elements tab (r211829)
  • Removed Shift-Command-W (⇧⌘W) shortcut to a close tab (r211485)


  • Fixed text string range from index and length in text controls when there are newlines (r211491)


  • Fixed column progression after enabling pagination on a right-to-left document (r211564)


  • Suspended SVG animations on hidden pages (r211612)
  • Avoided initially creating a layer backing store for elements outside the visible area (r211845)


  • Changed CSS data URL resources to be treated as same origin loads when loaded through HTML <link> elements (r211926)