Safari Technology Preview 243 FAQ: Features, Fixes, and Improvements

Apple has released Safari Technology Preview 243, the latest test version of its browser, available for macOS Tahoe and macOS Sequoia. This update brings a range of WebKit enhancements—from accessibility tweaks to CSS and animation refinements. Below, we answer the most common questions about this release, covering new features, resolved issues, and how to get the update.

What are the major accessibility improvements in this update?
How does this release address CSS animation issues?
What new CSS features were introduced in Safari Technology Preview 243?
What key CSS bugs were fixed in the area of layout and rendering?
Are there any improvements for CSS selectors and performance?
How can I download or update to this version?

What are the major accessibility improvements in this update?

Several accessibility issues have been resolved in Safari Technology Preview 243. Notably, the contextmenu event now correctly fires for elements inside iframes when triggered by keyboard or assistive technologies like VoiceOver’s VO+Shift+M action (bug 164128676). Additionally, color picker inputs can now be activated using VoiceOver’s press action (bug 172218114). A fix was applied to invalidation of aria-hidden="true" when focus lands inside the aria-hidden subtree (bug 174449524). Support for base <select> elements with VoiceOver has been enhanced: the popover now closes upon selection and the accessibility path correctly accounts for CSS transforms (bug 175058883). These changes make web content more usable for people relying on screen readers and keyboard navigation.

Safari Technology Preview 243 FAQ: Features, Fixes, and Improvements — Source: webkit.org

How does this release address CSS animation issues?

Two animation-related bugs have been fixed. First, !important declarations now properly override CSS animation values even when CSS transitions are running on the same property (bug 174367827). Previously, the animation would incorrectly take precedence. Second, an issue with identity matrix decomposition was corrected: it was generating invalid quaternions, which led to incorrect transform animations (bug 174813328). Now transform animations behave as expected, ensuring smoother visual effects. These fixes improve the reliability of CSS animations and transitions in web development.

What new CSS features were introduced in Safari Technology Preview 243?

Two new CSS capabilities have been added. First, contain: style now applies to CSS quote counters, as specified in CSS Containment Level 2 (bug 84758186). This gives developers finer control over style containment and improves performance in certain scenarios. Second, support for the insert keyword for the text-autospace property was added (bug 175031507). This property controls automatic spacing between characters, and the insert value enables insertion of spaces in specific contexts. Both additions align Safari more closely with ongoing CSS standards.

What key CSS bugs were fixed in the area of layout and rendering?

Several layout and rendering issues were resolved. In flex layout, the used flex-basis value (instead of the specified one) is now considered for definiteness evaluation (bug 85707621). Fixed an issue where element positioning was incorrect when the containing block was an anonymous block (bug 96548847). box-shadow now works on display: table-row elements (bug 96914376). The text-indent property with calc() containing percentages correctly treats percentage components as zero for intrinsic size contributions (bug 97025949). Out-of-flow content with fit-content now has the correct height (bug 97492632). Percentage size resolution in flex items in quirks mode was fixed (bug 100183902). clip-path: inset() border-radius values render correctly at different sizes (bug 110847266). -webkit-box flexbox emulation now correctly sizes children inside <fieldset> elements (bug 114094538). Elements with display: table and borders have correct layout (bug 116110440). Also, elements with border, position: absolute, and aspect-ratio: 1 now render as squares.

Are there any improvements for CSS selectors and performance?

Yes, performance on pages using :where and :is selectors has been improved (bug 114904007). These selectors, often used in modern CSS to apply styles conditionally, can become expensive when used extensively. The optimization reduces the processing overhead, leading to faster rendering and better responsiveness on complex web pages. This is part of ongoing efforts to keep Safari’s engine efficient as CSS evolves.

How can I download or update to this version?

Safari Technology Preview 243 is available for download for macOS Tahoe and macOS Sequoia. If you already have Safari Technology Preview installed, you can update it by going to System Settings > General > Software Update. The new version will appear as an available update. Alternatively, you can download the latest release directly from Apple’s developer website. The release includes WebKit changes from revision 310600 to 312007. Always ensure your macOS is compatible before updating.

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