WebKit Features in Safari 16.3

Today we are pleased to announce Safari 16.3, our first release of many coming this year. With it, WebKit provides multiple bug fixes and feature polish.


  • Fixed MediaQueryList.matches to update the parent document layout for viewport-dependent media queries.
  • Fixed transfers of min and max sizes for CSS aspect-ratio to be constrained by defined sizes.
  • Fixed gap to be accounted for by using the unclamped subgrid track sizes to compute track positions.
  • Fixed calculating block size to use the correct box-sizing.
  • Fixed the transferred min and max sizes to be constrained by defined sizes.
  • Fixed: Use intrinsic ratio of replaced elements when computing flex sizes.
  • Fixed negative content sizes when using box-sizing: border-box with border and padding.
  • Fixed setting scrollTop on a fixed element with overflow breaking scrolling on a page with overscroll-behavior: none.


  • Fixed replaced elements with aspect ratio and size in one dimension to respect the min and max constraints in the opposite dimension.


  • Fixed decompressing content downloaded via fetch() with Content-Encoding: gzip set.
  • Fixed downloads served from a service worker that uses preload.
  • Fixed: Added an error event when link preload fails synchronously.
  • Fixed Cross-Origin-Embedder-Policy incorrectly blocking scripts.
  • Fixed Authorization header used for subsequent 301 redirects when the request header changes.
  • Fixed showing a dialog element when the target is a shadow host with a focus delegates.

Content Security Policy

  • Added support for the prefetch-src directive.
  • Fixed: Check for strict-dynamic in script-src and default-src directives.
  • Fixed: Added an error event when Content Security Policy blocks inline stylesheets.


  • Fixed web audio becoming garbled with switching from speakers to headphones.
  • Fixed video track’s size settings in the second MediaStream created when the aspectRatio constraint is applied.
  • Fixed showing Media Session API artwork.
  • Fixed “A MediaStreamTrack ended due to a capture failure” error when selecting bluetooth headphones as an audio input device.
  • Fixed WebVTT styles to apply with in-band tracks.
  • Fixed alternate VPx codec names to support vp8.0 and vp9.0.


  • Fixed MouseClick offsetX and offsetY on a foreign object in an SVG to be relative to the element rather than relative to the SVG container.


We love hearing from you. Send a tweet to @webkit to share your thoughts on Safari 16.3. Find us on Mastodon at @jensimmons@front-end.social and @jondavis@mastodon.social. If you run into any issues, we welcome your feedback on Safari UI, or your WebKit bug report about web technology or Web Inspector. Filing issues really does make a difference.

Download the latest Safari Technology Preview to stay at the forefront of the web platform and to use the latest Web Inspector features. You can also read the Safari 16.3 release notes.

Updating to Safari 16.3

Safari 16.3 is available for macOS Ventura, macOS Monterey, macOS Big Sur, iPadOS 16, and iOS 16. You can update to Safari 16.3 on macOS Monterey or macOS Big Sur by going to System Preferences → Software Update → More info, and choosing to update Safari. To update macOS Ventura, iOS or iPadOS, go to Settings → General → Software Update.