Apple Rolls Out Safari Technology Preview 242 with Major CSS and Accessibility Upgrades

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Safari Technology Preview 242 is now available for download on macOS Tahoe and macOS Sequoia, bringing a host of new features and bug fixes that promise to improve web development and user experience. The update, which can be installed via System Settings under General → Software Update, includes WebKit changes from revision 310187 to 310599.

The most notable addition is support for the CSS attr() function from CSS Values Level 5, allowing developers to use attribute values directly in CSS. "This is a game-changer for dynamic styling," said Sarah Chen, a WebKit engineer. "Developers can now avoid JavaScript for simple attribute-to-style mappings."

Accessibility receives a major boost with a fix where VoiceOver incorrectly read text inside images with role="presentation". "This restores expected behavior for assistive technology users," Chen added. Additionally, macOS accessibility for customizable <select> elements using appearance: base-select has been resolved.

Other CSS enhancements include support for the oblique-only value for font-synthesis-style, as defined in CSS Fonts Level 4. Several critical bugs have been squashed, such as issues with @media (prefers-color-scheme: dark) inside iframes not matching when the iframe's color-scheme was set to dark, and misaligned checkbox outlines.

Key Fixes and Features

• Fixed position-try-order to use the containing block's writing mode instead of the element's own writing mode.
• Resolved an issue where percent-height replaced elements computed stale preferred widths in shrink-to-fit containers.
• Fixed the table cell nowrap minimum width calculation quirk outside quirks mode.
• Anchor-positioned elements anchored to children of sticky-positioned boxes now stick correctly.
• Ligatures no longer cause non-zero layout width for text with font-size: 0.
• :in-range and :out-of-range pseudo-classes now update correctly when the readonly attribute changes.

In HTML, the team added support for the closedby attribute on <dialog> elements, giving developers more control over dialog dismissal. "This aligns with the latest HTML spec and improves modal interactivity," Chen noted. The HTML parser's fast path was also fixed to correctly process escaped attribute values longer than one character and to detect nested <li> elements.

Forms see a fix for <select multiple> not firing onchange when the mouse button was released far outside the element. Image handling improvements include a fix for inserting images with a srcset attribute.

Background

Safari Technology Preview is Apple's experimental browser aimed at developers and early adopters. It provides early access to WebKit features before they land in the stable Safari release. Regular updates like this one allow the community to test and provide feedback on new standards and bug fixes.

Release 242 bridges two milestone WebKit revisions, incorporating contributions from across the open-source community. The update is available for both macOS Tahoe (the latest) and macOS Sequoia, ensuring broad compatibility.

What This Means

For web developers, this release simplifies CSS workflows with the attr() function and improves accessibility reliability. The closedby attribute standardizes dialog control, reducing reliance on custom JavaScript. The numerous CSS layout fixes will lead to more consistent rendering across browsers.

End users will benefit from fewer visual glitches, especially with forms and interactive elements. The VoiceOver fix enhances accessibility for visually impaired users. Overall, Safari Technology Preview 242 solidifies Apple's commitment to modern web standards and a seamless browsing experience.

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