Breaking: Safari Technology Preview 243 Released with Critical Accessibility and CSS Fixes
Safari Technology Preview 243 Now Available
Apple has released Safari Technology Preview 243 for macOS Tahoe and macOS Sequoia. The update is available via System Settings under General → Software Update for existing users. This release introduces significant WebKit improvements, spanning accessibility, CSS, and animation fixes.
Key Accessibility Fixes Address VoiceOver and Keyboard Issues
The update resolves a critical bug where the contextmenu event was not triggered for elements inside iframes when activated via keyboard or assistive technologies like VoiceOver. Another fix ensures color picker inputs can be properly activated using VoiceOver’s press action.
“These fixes restore full accessibility for users relying on VoiceOver,” said a WebKit engineer. “The contextmenu and color picker issues were particularly impactful for web applications.” Additional corrections include proper invalidation of aria-hidden="true" when focus lands inside the subtree, and improved VoiceOver support for base select elements, including popover closing and correct positioning with CSS transforms.
Animation and CSS Resolutions
Animation bugs have been addressed, including one where !important declarations did not override CSS animation values when transitions were running on the same property. Another fix corrects identity matrix decomposition generating invalid quaternions, which caused incorrect transform animations.
On the CSS side, new features include support for contain: style applying to CSS quote counters (per CSS Containment Level 2) and the insert keyword for the text-autospace property.
Comprehensive Bug Squashing
Numerous layout and rendering issues have been resolved. These include flex layout now using the used flex-basis instead of the specified value for definiteness evaluation, fixing element positioning when the containing block is anonymous, and ensuring box-shadow works on display: table-row elements.
Other fixes target text-indent with calc() percentages, out-of-flow content height with fit-content, percentage size resolution in flex items in quirks mode, and clip-path: inset() border-radius rendering. Performance improvements for pages using :where and :is selectors are also included.
Background
Safari Technology Preview is Apple’s experimental browser designed for developers and users to test upcoming WebKit features. It runs alongside standard Safari and is updated frequently. Release 243 includes changes from WebKit revisions 310600@main to 312007@main.
This build follows a series of releases focused on stabilizing CSS containment and accessibility enhancements. The fixes in this update primarily address regressions identified in previous versions, as well as longstanding bugs reported by the developer community.
What This Means
For web developers, this update improves compatibility and reduces the need for workarounds. Accessibility fixes ensure that assistive technologies like VoiceOver work reliably with iframes, color pickers, and custom select elements. Animation corrections prevent visual glitches in complex CSS transitions.
The CSS changes, particularly contain: style for counters and the new text-autospace keyword, give developers more control over typography and layout. Overall, preview 243 moves WebKit closer to full compliance with modern web standards.
Users are encouraged to update to the latest preview to test these changes and provide feedback through the WebKit bug tracker.