Safari Technology Preview 242: Key Updates and Enhancements

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Welcome to the latest look at web technologies with Safari Technology Preview 242. This release brings important fixes and new features, especially for CSS and accessibility. Whether you're a developer testing web standards or an enthusiast exploring the future of Safari, this update has something for you. Here are the top questions answered about this release.

What is Safari Technology Preview 242 and how can I install it?

Safari Technology Preview 242 is the newest experimental version of Safari, designed for developers to test upcoming web features. It's available for macOS Tahoe and macOS Sequoia. If you already have the Technology Preview installed, updating is simple: open System Settings, go to General > Software Update. This release includes WebKit changes from build 310187 to 310599. It’s a great way to get early access to improvements that will later appear in the stable version of Safari.

What accessibility issues were fixed in this update?

This release tackles two key accessibility problems. First, VoiceOver no longer reads text inside images that have role="presentation" — a fix that prevents confusing announcements for assistive technology users. Second, macOS accessibility now properly supports customizable <select> elements using the appearance: base-select CSS property. This means developers can style dropdowns more freely without breaking screen reader support. These fixes ensure a smoother experience for users relying on VoiceOver and other assistive tools.

Which new CSS features are introduced?

Two notable CSS additions debut in this release. First is support for the attr() function from CSS Values Level 5, allowing you to fetch attribute values directly in CSS — useful for dynamic styling without JavaScript. Second, the oblique-only value for font-synthesis-style is now supported, as defined in CSS Fonts Level 4. This lets you control whether a browser can synthesize an oblique (slanted) font variant only when a true oblique font isn’t available. Both features expand your styling toolkit while staying true to the evolving CSS specifications.

What critical CSS bugs were resolved?

Several important CSS issues were fixed. Among them:

• @media (prefers-color-scheme: dark) now correctly matches inside iframes when the iframe’s color-scheme is set to dark.
• position-try-order now interprets logical axis values using the containing block’s writing mode, not the element’s own mode.
• Percent-height replaced elements in shrink-to-fit containers no longer compute stale preferred widths.
• The table cell nowrap minimum width calculation quirk is now limited to quirks mode, as intended.
• Checkbox outlines are no longer misaligned.
• Anchor-positioned elements anchored to children of sticky-positioned boxes stick correctly now.
• Pseudo-elements are sorted correctly when sorting anchor elements by tree order.
• Ligatures no longer cause a non-zero layout width for text with font-size: 0.
• :in-range and :out-of-range pseudo-classes update properly when the readonly attribute changes.
• View-timeline-inset serialization now coalesces identical values.

These fixes improve rendering accuracy and layout behavior across a wide range of scenarios.

How does this update improve forms and HTML?

Forms get a fix for <select multiple> elements: the onchange event now fires reliably even when the mouse button is released far outside the element. For HTML, the new closedby attribute on <dialog> elements gives developers more control over how dialogs are dismissed. Additionally, the HTML parser’s fast path was corrected to handle escaped attribute values longer than one character, detect nested <li> elements, and use the adjusted current node for MathML and SVG integration point checks. These parser fixes improve compatibility with complex markup.

What image-related fix is included?

For images, this release resolves an issue where inserting an image with a srcset attribute into the DOM could cause rendering problems. While details are brief, this fix ensures that responsive images using srcset behave correctly when added dynamically. If you work with adaptive images or content management systems that inject images into the page, this update will bring more predictable behavior.