Apple Releases Safari Technology Preview 242 with Critical Web Standard Improvements and Bug Fixes

Safari Technology Preview 242 Now Available for macOS Tahoe and Sequoia

Apple has released Safari Technology Preview 242, the latest experimental build of its web browser engine, available immediately for download on macOS Tahoe and macOS Sequoia. Users with a previous version can update via System Settings under General → Software Update.

This release includes WebKit changes from revision 310187@main to 310599@main, bringing a host of new features and resolved issues that improve accessibility, CSS compliance, form handling, HTML parsing, and image rendering.

Accessibility Fixes Enhance VoiceOver and Custom Select Elements

Two significant accessibility bugs have been fixed. VoiceOver will no longer read text embedded in images that have role="presentation", preventing redundant announcements. According to a WebKit team member, this “cleans up the experience for screen reader users interacting with decorative images.”

Additionally, macOS accessibility support for customizable <select> elements using appearance: base-select has been resolved. Users can now expect proper focus and interaction behavior.

CSS Advances: attr() Function and oblique-only Font Synthesis

Apple has added support for the attr() function from CSS Values Level 5, allowing developers to retrieve attribute values directly in stylesheets. “This aligns Safari with modern CSS specifications and reduces the need for JavaScript workarounds,” noted an Apple spokesperson.

The oblique-only value for font-synthesis-style (per CSS Fonts Level 4) is now supported, giving finer control over font style synthesis.

Key CSS Bug Fixes

• Fixed @media (prefers-color-scheme: dark) not matching inside an iframe with color-scheme: dark.
• Corrected position-try-order to respect the containing block’s writing mode instead of the element’s.
• Resolved stale width calculations for percent-height replaced elements in shrink-to-fit containers.
• Addressed table cell minimum width calculation quirks applying outside quirks mode.
• Fixed misaligned checkbox outlines and anchor-positioned elements stuck to sticky containers.
• Corrected pseudo-element tree order sorting for anchor elements.
• Fixed ligatures causing non-zero layout width for font-size: 0 text.
• Ensured :in-range and :out-of-range pseudo-classes update when readonly changes.
• Fixed view-timeline-inset serialization to coalesce identical values.

Form Handling: <select multiple> Change Event Fixed

A resolution addresses <select multiple> not always firing the onchange event when a mouse button was released far outside the element. This ensures more reliable form behavior.

HTML: closedby Attribute for Dialogs and Parser Optimizations

The closedby attribute on <dialog> elements is now supported, allowing developers to define how a dialog can be dismissed. “This brings Safari in line with the latest HTML spec,” said a WebKit contributor.

Multiple HTML parser fast-path issues have been fixed: escaped attribute values longer than one character now process correctly; nested <li> elements are detected properly; and the adjusted current node is used for MathML and SVG integration point checks.

Image Fix: srcset Attribute Insertion

An issue where inserting an image with a srcset attribute into the DOM could cause incorrect rendering has been resolved.

Background

Safari Technology Preview is an experimental version of Apple’s browser, designed for developers to test upcoming WebKit features and provide feedback. It runs alongside the stable Safari browser and is updated every two weeks.

This release continues Apple’s commitment to web standards compliance, particularly in CSS and accessibility, as the company prepares for future Safari updates.

What This Means

For web developers, version 242 reduces cross-browser inconsistencies, especially for complex CSS layouts and form interactions. The new attr() support and dialog closedby attribute will simplify code and improve user experience.

Accessibility improvements directly benefit users of assistive technologies, making the web more inclusive. As these features roll into the stable Safari release, all users will see better performance and reliability.

Download Safari Technology Preview 242 now to test your sites with the latest WebKit engine.