Exploring Safari Technology Preview 241: New Features and Fixes

Safari Technology Preview Release 241 is now available for download on macOS Tahoe and macOS Sequoia. If you already have it installed, you can update via System Settings under General → Software Update. This release includes WebKit changes from revision 309287 to 310186, bringing a host of improvements across accessibility, animations, and CSS. Below, we break down the key updates in a Q&A format to help you understand what’s new.

1. What accessibility issues were resolved in Safari Technology Preview 241?

Several important accessibility bugs were fixed. First, calling speechSynthesis.cancel() no longer removes utterances queued by subsequent speechSynthesis.speak() calls, ensuring smoother text-to-speech experiences. Additionally, incorrect bounding boxes for MathML table rows and cells have been corrected, which improves screen reader navigation. Combobox elements now properly forward focus to their aria-activedescendant, allowing assistive technologies to interact with list items. Finally, the aria-owns attribute is now respected when computing accessible names from element content, fixing a gap in name calculation.

2. How was the animation-fill-mode bug fixed in this release?

Animations using animation-fill-mode previously failed to correctly apply viewport-based units (like vw or vh) after the viewport was resized. This issue has been resolved by ensuring that the fill mode recalculates units upon viewport changes. This fix makes animations more reliable when used with responsive layouts, preventing visual glitches during window resizing.

3. What new CSS features were added in this update?

Two notable CSS features have been introduced. First, the stretch keyword is now supported in box sizing properties, allowing elements to stretch to fill their containing block without explicit width or height. Second, CSS scroll anchoring has moved to stable support, meaning the browser will now more reliably prevent content jumps when additional content loads above the current viewport. This stabilizes the user experience, especially on scroll-heavy pages.

4. Which CSS rendering issues were fixed in Safari Technology Preview 241?

Multiple rendering bugs were addressed. The outline-offset property is no longer inflated when outline: auto is used on macOS, ensuring consistent outline sizes. Font-family serialization now preserves quotes around family names that match CSS-wide keywords or generic families. Additionally, the browser no longer downloads a font if no characters in the document fall within its unicode-range, saving bandwidth. A flex item containing a percentage-height image now shrinks correctly, and view transition snapshots are no longer incorrectly stored in sRGB, which fixes color rendering with non-sRGB colors.

5. Were there any performance improvements in this release?

Yes, a significant performance issue was fixed where contain: layout caused dramatically slower forced layouts when all siblings created their own formatting context. This change improves rendering speed in complex layouts. Additionally, changing color-scheme now correctly repaints the background of composited iframes, preventing leftover colors. A fix for underlines being split when a ruby base expands due to long ruby text also improves text rendering performance.

6. What other rendering problems were solved?

Several other rendering issues were resolved. Nested children of a popover element using position: absolute failed to render; this is now fixed. The color: initial keyword no longer resolves to the wrong color in dark appearance mode. Elements with display: contents now properly establish an anchor scope when using anchor-scope. Finally, a regression where media queries could fail to resolve in certain conditions was corrected, ensuring responsive designs work as expected.