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Safari Technology Preview 34 for Mac Release Offers Bug Fixes and Performance Improvements

Safari Technology Preview 34 for Mac Release Offers Bug Fixes and Performance Improvements

Apple on Wednesday released Safari Technology Preview 34, a new version of their experimental web browser, first released in March 2016. The browser allows developers and other interested parties to test features that may debut in future release versions of Safari.

Safari Technology Preview 34 for Mac Release Offers Bug Fixes and Performance Improvements

Fixes in features in Safari Technology Preview 34 include:


  • Added WebRTC options to the Developer menu
  • Disabled Legacy WebRTC API in the Experimental Features menu by default
  • Changed behavior to close NetworkProcess WebRTC sockets as soon as the Web Process no longer needs them
  • Added support for receive-only SDP offers through addTransceiver
  • Changed handling capture status based on MediaStreamTrack
  • Changed RTCPeerConnection to return RTCSessionDescriptionInit instead of RTCSessionDescription
  • Fixed a cloned MediaStreamTrack to not mute the other tracks using the same source
  • Fixed RTCPeerConnection getReceivers() to return transceivers that have an active receiver but no active sender
  • Fixed the screen going into sleep mode during WebRTC video


  • Fixed high CPU usage when entering fullscreen or seeking during MSE video playback
  • Fixed seeking during MSE video playback where audio would begin playing long before rendering the video
  • Fixed video flashing black when switching back to a tab
  • Improved media controls rendering for long-loading media files
  • Prevented media elements continuing to load media data after navigation


  • Made Object.assign faster by rewriting it in C++
  • Reduced Structure size
  • Updated RegExp.prototype.[@@search]] implementation according to the latest specifications
  • Fixed PreTypedArray constructor with a string to not throw an exception


  • Applied img-src CSP directive to favicon loads
  • Implemented W3C Secure Contexts Draft Specification
  • Restricted filtered painting across cross-origin boundaries with transforms
  • Added allow-popups-to-escape-sandbox attribute support for <iframe> elements
  • Added Subresource Integrity as an experimental feature

Web Inspector

  • Added grid to image previews to clarify transparency and image size
  • Fixed console message icons that overlap the source location
  • Fixed pretty print, type info, and code coverage buttons disappearing after switching tabs
  • Fixed SVG files and favicon files that don’t display properly
  • Fixed the search highlight not showing up in resources when paused
  • Fixed showing non-shadow children of an element with a shadow root (e.g. <video>)


  • Fixed the meter element not respecting the writing direction
  • Fixed WebGPU contexts to have a back reference to the canvas element
  • Fixed CSS transitions added while page is not visible so they start animating when the page becomes visible
  • Fixed IndexedDB.getAll() use inside a Web Worker


  • Moved SubtleCrypto from the experiemental features menu
  • Removed unsupported AES_CMACDH, and CONCAT


  • Fixed several miscellaneous bugs found from web platform tests


  • Added an experimental feature setting for asynchronous frame scrolling


  • Exposed the inline property as an accessibility attribute

Bug Fixes

  • Fixed mint.com header rendering incorrectly when initially loaded
  • Fixed scrubbing backward on a YouTube video

Users can either download the update from the Safari Technology Preview website, or if they already have the browser installed, they can download it via the Mac App Store. Full release notes for the update are available on the same website.

While the preview is intended for use by developers and advanced users, in order to provide Apple with feedback on the development of the Safari browser, it can be run side-by-side with the release version of Safari. The app doesn’t require a developer account to download and install. For more information, visit the Safari Tech Preview website.