Release Notes for Safari Technology Preview 118

Safari Technology Preview Release 118 is now available for download for macOS Big Sur and macOS Catalina. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS.

This release covers WebKit revisions 270230-270749.

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 (r270551, r270618)
  • 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 (r270552, r270371)
  • 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 (r270641, r270290, r270294, r270507, r270532)
  • 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