Safari Technology Preview 241: Key Updates and Improvements in WebKit
Welcome to the latest Safari Technology Preview release! Version 241 brings a host of refinements and new capabilities designed to make the web more accessible, performant, and developer-friendly. Whether you're a web developer, accessibility advocate, or just curious about the latest web standards, this update has something for you. Below, we answer the most pressing questions about what's changed, from accessibility fixes to CSS enhancements.
What is new in Safari Technology Preview 241?
This release, available for macOS Tahoe and Sequoia, includes WebKit changes from version 309287 to 310186. It resolves numerous bugs and adds several features. Key highlights include improvements to accessibility—like fixing speech synthesis cancellation issues and better support for ARIA attributes—and CSS updates, such as stable support for CSS scroll anchoring and the new stretch keyword for box sizing. Performance is also boosted by addressing contain:layout slowdowns and font download optimizations. To get it, update via System Settings → General → Software Update if you already have the preview installed, or download it fresh from Apple.
How does this release improve accessibility?
Accessibility gets several focused fixes. For example, calling speechSynthesis.cancel() no longer removes utterances queued by later speechSynthesis.speak() calls, ensuring smoother text-to-speech experiences. MathML table rows and cells now compute correct bounding boxes, helping screen readers interpret complex equations. Comboboxes now correctly forward focus to their aria-activedescendant, letting assistive technologies interact with list items. Additionally, the aria-owns attribute is now properly respected when computing accessible names from element content, making custom widgets more discoverable. These changes collectively improve the reliability of voice-over and other assistive tools.
What animation issue was resolved?
A specific bug in animation-fill-mode has been fixed. Previously, when using viewport-based units in fill-mode values, the animation wouldn't correctly update after resizing the viewport. For instance, if a @keyframes rule used 100vw for a property, the fill state remained at the original width instead of adjusting. Now, it recalibrates properly, ensuring responsive animations behave as expected when the browser window changes size.
What new CSS features are introduced?
Two notable additions: first, the stretch keyword for box-sizing properties. This lets elements fill available space in a more intuitive way, similar to how flex-grow works but for block-level containers. Second, CSS scroll anchoring is now stable. This feature prevents jarring jumps when content above the viewport loads (e.g., ads or images), by automatically adjusting the scroll position. It’s a major quality-of-life improvement for reading long pages with dynamic content.
What are some important CSS bug fixes?
Several bugs were resolved: The U+2028 LINE SEPARATOR now renders as a forced line break per the CSS spec. On macOS, outline: auto no longer inflates outline-offset incorrectly. Font-family serialization preserves quotes around names matching CSS-wide keywords or generic families. A bug where fonts were downloaded even without matching characters (based on unicode-range) has been fixed. Flex items with percentage-height images now shrink correctly. View Transition snapshots are stored in correct color space instead of incorrectly in sRGB, fixing rendering with non-sRGB colors. Also, changing color-scheme now repaints composited iframe backgrounds, and nested children of a popover element with position: absolute render properly. The color: initial value now resolves to the correct color in dark mode, and display: contents elements create anchor-scope scopes. A regression where media queries failed to resolve has also been addressed.
What performance improvements are included?
One key fix addresses a performance issue with contain: layout. When all siblings in a container created their own formatting context, forced layouts became significantly slower. By optimizing the containment logic, this version cuts down that overhead, making pages with complex layouts more responsive. Additionally, the font download fix (no longer fetching unused font files) reduces network traffic and speeds up page load times. These improvements together make Safari Technology Preview 241 smoother for web apps and content-rich sites.
How can I update to Safari Technology Preview 241?
If you already have Safari Technology Preview installed on macOS Tahoe or Sequoia, simply go to System Settings → General → Software Update and check for updates. The new version will appear as Safari Technology Preview 241. If you don't have it yet, you can download the installer from Apple's developer portal. This release includes all WebKit changes up to revision 310186, ensuring you have the latest features and fixes for testing and development.