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Safari Technology Preview 118 Release Offers Bug Fixes and Performance Improvements

Safari Technology Preview 118 Release Offers Bug Fixes and Performance Improvements

Apple on Wednesday released Safari Technology Preview 118, the latest version of their developer preview web browser. The preview version of Apple’s popular browser offers developers and other interested users the ability to try out features that may or may not, debut in future public release versions of Safari.

‌Safari Technology Preview‌ release 118 brings bug fixes and performance improvements for Web Inspector, CSS, Scrolling, JavaScript, WebGL, Media, Private Click Measurement, WebRTC, Web API, Accessibility, and Extensions.

The current ‌Safari Technology Preview‌ release is built on the new Safari 14 update included in macOS Big Sur.

Release 118

Web Inspector

  • Elements
    • Added an experimental Font details sidebar panel for showing information about the currently used font of the selected node (r270637)
  • Sources
    • Added support for intercepting and overriding network requests (r270604)


  • Implemented Definite and Indefinite Sizes in flexbox (r270578)
  • Corrected cases in which box-sizing was border-box and didn’t use the content box to compute size based on aspect ratio (r270617)
  • Fixed preserving aspect ratio when computing cross size of flexed images in auto-height flex container (r270288)
  • Added support for aspect-ratio on replaced and non-replaced elements (r270551r270618)
  • Changed text-decoration-color animation not to be discrete (r270597)
  • Changed getComputedStyle rounding lineHeight to nearest pixel (r270248)
  • Changed to trigger web font loads earlier (r270590)


  • Made only the first wheel event in a gesture to be cancelable (r270425)


  • Enabled “at” methods (r270550)
  • Changed get and set for object literal and class to not be escaped (r270487)
  • Accepted escaped keywords for class and object property names (r270481)
  • Aligned %TypedArray% constructor/slice behavior with the specification strictly (r270552r270371)
  • Added a JSC API to allow acquiring the JSLock to accelerate performance (r270659)
  • Removed unnecessary JSLock use from various JSC APIs (r270665)
  • Aligned [[DefineOwnProperty]] method of mapped arguments object with the specification strictly (r270664)
  • Changed Reflect.preventExtensions not throwing if called on WindowProxy or Location (r270702)


  • Fixed rasterizer discard interfering with implicit clears in WebGL 2 (r270253)


  • Implemented WebVTT VTTCue region attribute (r270738)

Private Click Measurement

  • Exposed an API for enabling or disabling Private Click Measurement (r270710)


  • Added support for RTCRtpSender::setStreams (r270486)
  • Enabled use of new socket API for WebRTC TLS connections by default (r270680)
  • Fixed ICE not resolving for turns relay candidates rooted in LetsEncrypt CA (r270626)
  • Improved RTCRtpSender and RTCRtpReceiver transforms support (r270641r270290r270294r270507r270532)
  • Introduced an experimental flag specific to VP9 profile 2 (r270256)


  • Changed to allow blob URLs with fragments (r270269)
  • Fixed lazy loaded iframe to not lazy load when scripting is disabled (r270300)
  • Changed Reflect.preventExtensions to not throw if called on WindowProxy or Location (r270702)
  • Changed sessionStorage to not be cloned when a window is opened with rel=noopener (r270273)
  • Updated the list of blocked ports according fetch specification (r270321)


  • Fixed VoiceOver not announcing the aria-checked state for ARIA treeitem (r270333)


  • Fixed the onClicked listener not being called for page actions

The preview is available for both macOS Catalina and macOS Big Sur.

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 Technology Preview website.