Safari Technology Preview 240: Key Updates and Bug Fixes

Introduction

Apple has released Safari Technology Preview 240, the latest experimental version of its web browser, now available for macOS Tahoe and macOS Sequoia. This update brings a host of improvements aimed at refining CSS capabilities, enhancing editing experiences, fixing form behavior, correcting HTML parsing, and expanding media support. For existing users, the update can be applied via System Settings under General → Software Update. Below, we explore the most notable changes in this release.

Safari Technology Preview 240: Key Updates and Bug Fixes — Source: webkit.org

CSS Enhancements

New CSS Features

The highlight of this release is the addition of the revert-rule keyword. This new CSS keyword allows developers to roll back the cascade for a specific rule, effectively making the browser behave as if the rule were never applied. This provides finer control over style inheritance and cascading behavior, particularly useful in complex stylesheets.

Resolved CSS Issues

Custom scrollbar clipping: On macOS, custom CSS scrollbars were sometimes cut off, and the scrollbar corner rectangle was sized incorrectly. This has been fixed, ensuring scrollbars render accurately.
Hanging punctuation enhancements: The hanging-punctuation property now correctly supports the apostrophe (U+0027) and quotation mark (U+0022) as hangable characters. Additionally, ideographic space (U+3000) can now hang when used with the first value, aligning with typographic expectations.

Editing Improvements

Several bugs affecting text editing have been resolved, making the experience smoother for users:

Font Picker usability: After changing fonts while editing multiple lines of text, the Font Picker style selection became unresponsive. This issue is now fixed.
Emoji preservation in copy-paste: Emoji images were not being preserved correctly when copying and pasting content across different websites. This has been addressed, ensuring emojis stay intact.
Text selection jumps: When selecting absolutely-positioned content inside an element with user-select: none, the text selection would unexpectedly jump. This behavior has been corrected.

Forms Fixes

A single but impactful fix targets form navigation: when a focused button becomes disabled, keyboard tabbing position was lost, causing the focus to jump to the beginning of the page. Now, the tab order is preserved, improving accessibility and user flow.

HTML Parser Corrections

Two parsing issues have been resolved:

Viewport meta tag: The parser now correctly treats the form feed character as ASCII whitespace, as required by the HTML specification. This ensures more consistent viewport processing.
Pixel-length margin attributes: On elements like <body>, <iframe>, and <frame>, pixel-length margin attributes were being parsed incorrectly. This has been fixed to align with expected behavior.

Media Updates

Media playback and decoding have received multiple fixes, broadening compatibility and reliability:

WebM audio with multiple channels: Decoding WebM audio files with more than two channels would fail. This is now resolved.
VP8 in WebM detection: MediaCapabilities.decodingInfo() was incorrectly reporting VP8 in WebM as unsupported. This has been corrected.
Opus audio in MP4: MP4 files containing Opus audio tracks could not be decoded using decodeAudioData. This issue is fixed.
Live Text in fullscreen video: Live Text selection was unavailable on paused fullscreen videos; it now works as expected.
FairPlay-protected VP9: FairPlay-protected VP9 content failed to play via MediaSource. This has been resolved.
Autoplay timing: Autoplay would proceed before default text tracks finished loading, causing synchronization issues. This is now fixed.
currentTime getter: The currentTime getter now returns defaultPlaybackStartPosition when no media player exists, improving consistency.
timeupdate event: HTMLMediaElement now fires a timeupdate event when resetting the playback position during media load, complying with the specification.

Conclusion

Safari Technology Preview 240 continues Apple’s commitment to refining the web platform. With enhancements across CSS, editing, forms, HTML, and media, developers and early adopters can expect a more robust browsing experience. As always, these improvements are a step toward greater standards compliance and user satisfaction. For a complete list of changes, refer to the official release notes. Back to top