Apple has pushed out its fist update to the recently launched Safari Technology Preview, a version of Safari aimed squarely at developers. The update comes exactly two weeks after Safari Technology Preview's March 30 launch, and includes a slew of updates and changes across the board.

Browser Differences

  • Changed the CFBundleSignature to allow Apple Events, like those sent from AppleScript, to correctly distinguish between Safari and Safari Technology Preview


  • Added ES6 support for Symbol.isConcatSpreadable
  • Disallowed var assignments in for-in loops according to ES6 specs
  • Improved stability for ES6 classes when invoking a method of the parent class before calling super() in a constructor
  • Allowed undefined or null for and Symbol.match
  • Enabled Array.prototype native functions' species constructors to work with proxies
  • Implemented the proposal for String.prototype.padStart() and String.prototype.padEnd()
  • Implemented ES6 spec for String.prototype.match and RegExp.prototype[@@match]
  • Included a workaround for web compatibility on ES6 TypeErrors when accessing RegExp.prototype flag properties
  • Corrected quantified unicode regular expressions
  • Ensured greedy unicode regular expressions properly backtrack past non-BMP characters


  • Implemented the allow-end value of the hanging-punctuation CSS property
  • Improved web compatibility by resetting CSS spacing rules on elements
  • Added the new color-gamut CSS media query
  • Updated screen queries to check the capabilities of the current screen instead of the deepest available screen

Web APIs

  • Restricted WebSockets header parsing according to RFC6455 and RFC7230
  • Improved performance of certain draw calls in WebGL with a non-power-of-two texture optimization
  • Disabled the Fetch API until the implementation is ready to be enabled by default
  • Enhanced Shadow DOM support to compute styles for the style attribute of elements
  • Softened pushState and replaceState frequency restrictions

Web Inspector

  • Timelines tab performance and bug fixes
  • Disabled debugger statements while profiling a page to ensure maximum performance accuracy
  • Added the ability to configure timeline instruments to use for recordings
  • Added a paint count indicator in the top left corner of non-opaque layers
  • Added font-variant-numeric to CSS autocompletions
  • Added the console.takeHeapSnapshot method for capturing heap snapshots
  • Changed details sidebar shortcuts to Command-Option-0 and Command-Shift-0
  • Double-quotes and backslashes in strings are now displayed correctly in the console
  • Improved the consistency of CSP directive violation messages reported in the console


  • Corrected new lines in content editable elements to notify accessibility
  • Updated the handling of SVG elements with a presentational role to be the same as other host language elements
  • Limited the numbered list announcement for a list item number to the first line of text in the list item
  • Changed the accessibility role descriptions for JavaScript alerts to "web dialog" and "web alert dialog" to make them more understandable to screen reader users


  • Updated backdrop filter to repaint when changed in JavaScript
  • Corrected drawing SVG stroke patterns for objects with empty bounding box elements


  • Improved stability when an audio source is changed while being processed
  • Fixed audio track listings


  • Improved the reliability of speculative disk cache validation requests with the HTTP Referer header

Bug Fixes

  • Fixed autoscrolling in a drag selection when a window is against the screen edge, including while in full screen mode

To recap, Safari Technology Preview is meant to give developers a way to experiment with and test new technologies before they make their way to Safari proper. If you're interested in testing it, Safari Technology Preview can be downloaded from Apple{.nofollow}. If you have the previous version of the Preview, you can grab the update from the Mac App Store.

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