Apple Releases Safari Technology Preview 243 with Critical Accessibility and CSS Fixes
Safari Technology Preview 243 is now available for download for macOS Tahoe and macOS Sequoia. The update brings essential bug fixes and new features targeting accessibility, CSS, and animations.
Users with a previous version can install the update through System Settings → General → Software Update. This release incorporates WebKit changes spanning commits 310600 to 312007.
Key Accessibility Resolutions
“We resolved a critical issue where the contextmenu event was not fired for elements inside iframes when triggered by keyboard or assistive technology actions like VoiceOver’s VO+Shift+M,” said an Apple spokesperson. The fix ensures that users relying on keyboard navigation or screen readers can now access context menus inside embedded frames.
VoiceOver users also faced a problem with color picker inputs that could not be activated. That bug has been resolved, allowing color selection through VoiceOver’s press action. Additionally, the team fixed a scenario where aria-hidden="true" was incorrectly invalidated when focus moved inside the hidden subtree, improving ARIA compliance.
Base <select> elements now fully support VoiceOver, including closing the popover upon selection and correctly positioning the accessibility path when CSS transforms are applied. “These fixes directly enhance the browsing experience for users with disabilities,” the spokesperson added.
Animation and CSS Improvements
Developers will appreciate the fix for !important declarations overriding CSS animation values when transitions are also running on the same property. An issue where identity matrix decomposition generated invalid quaternions—causing incorrect transform animations—has also been resolved.
The release introduces support for contain: style applied to CSS quote counters, as specified in CSS Containment Level 2. This improves performance by limiting the scope of style calculations. Additionally, the insert keyword for the text-autospace property is now supported, giving developers finer control over text spacing.
Several layout bugs have been squashed: Flex layout now uses the used flex-basis instead of the specified value for definiteness evaluation. Element positioning no longer breaks when the containing block is an anonymous block. Box-shadow now works on display: table-row elements. Text-indent with calc() containing percentages correctly treats percentage components as zero for intrinsic size contributions.
Additional fixes address incorrect height for out-of-flow content set to fit-content, percentage size resolution in flex items in quirks mode, and clip-path: inset() border-radius rendering at certain sizes. The -webkit-box flexbox emulation now correctly sizes children inside <fieldset> elements. Performance on pages using :where and :is selectors has been improved.
Background: What Is Safari Technology Preview?
Safari Technology Preview is a browser designed for developers and early adopters to test new WebKit features before they appear in the main Safari browser. It is released by Apple roughly every two weeks and includes experimental technologies, bug fixes, and performance enhancements. Because it runs alongside the standard Safari, users can safely evaluate changes without affecting their primary browser.
This preview version is essential for web developers who need to ensure their sites are compatible with upcoming standards. It also provides a vital feedback channel for Apple’s WebKit team to catch regressions early.
What This Means for Developers and Users
For developers, the fixes related to aria-hidden and VoiceOver accessibility ensure that web applications comply with modern accessibility guidelines, reducing the risk of lawsuits and improving user experience for people with disabilities. The CSS improvements, such as contain: style, offer better performance and more predictable rendering.
Users of assistive technology will notice fewer glitches when interacting with forms, context menus, and color pickers. Meanwhile, animation stability means fewer visual artifacts in web apps that rely on CSS transitions.
“We encourage all developers to update to Safari Technology Preview 243 and test their content,” the spokesperson urged. “The changes here represent a significant step forward in both accessibility and core web rendering.”
For a complete list of changes, including all resolved WebKit issues, refer to the official release notes. The update is available now for macOS Tahoe and macOS Sequoia.