Safari Technology Preview 242: Enhanced CSS Capabilities and Key Fixes

Introduction

Apple has released Safari Technology Preview 242, available for download on macOS Tahoe and macOS Sequoia. Existing users can update via System Settings → General → Software Update. This build incorporates WebKit changes from revision 310187 to 310599, bringing a host of improvements in accessibility, CSS, forms, HTML, and image handling.

Accessibility Enhancements

VoiceOver Fix

A resolved issue ensures that VoiceOver no longer reads text within images that have role="presentation", improving screen reader behavior for decorative images.

Customizable Select Elements

macOS accessibility support for customizable <select> elements using appearance: base-select has been fixed, enhancing the usability of styled dropdowns for assistive technologies.

CSS Improvements

New CSS attr() Function

Support has been added for the attr() function from CSS Values Level 5, allowing developers to retrieve attribute values directly in CSS—a powerful tool for dynamic styling.

Font Synthesis Style: oblique-only

The oblique-only value for font-synthesis-style is now supported, as defined in CSS Fonts Level 4, giving designers finer control over font rendering.

Resolved CSS Issues

• Dark mode in iframes: @media (prefers-color-scheme: dark) now correctly matches inside iframes with color-scheme: dark.
• Position try order: Logical axis values in position-try-order are now interpreted using the containing block's writing mode, not the element's own mode.
• Percent-height replaced elements: Stale preferred widths in shrink-to-fit containers no longer occur.
• Table cell nowrap: The minimum width calculation quirk for nowrap is no longer applied outside quirks mode.
• Checkbox outlines: Misaligned outlines on checkboxes have been corrected.
• Anchor positioning with sticky: Elements anchored to children of sticky boxes now stick correctly.
• Pseudo-elements sorting: Tree-order sorting of anchor elements now works properly for pseudo-elements.
• Ligatures and font-size: 0: Ligatures no longer cause non-zero layout width for text with font-size: 0.
• :in-range and :out-of-range: These pseudo-classes update correctly when the readonly attribute changes.
• View-timeline-inset: Serialization now correctly coalesces identical values.

Forms Fixes

<select multiple> now reliably fires the onchange event when the mouse button is released far outside the element, improving form interaction.

HTML Updates

New closedby Attribute for Dialogs

Support has been added for the closedby attribute on <dialog> elements, providing a standardized way to control dialog dismissal behavior.

HTML Parser Fixes

• The fast path now correctly processes escaped attribute values longer than one character.
• Nested <li> elements are properly detected.
• Checks for MathML and SVG integration points now use the adjusted current node, preventing parser errors.

Image Handling

An issue where inserting an image with a srcset attribute could cause rendering errors has been resolved, ensuring smoother responsive image loading.

Conclusion

Safari Technology Preview 242 continues Apple’s commitment to web standards and developer experience. With new CSS capabilities, accessibility refinements, and numerous bug fixes, this release helps create a more robust and consistent browsing environment. Developers and early adopters are encouraged to test their sites with this build and provide feedback.