Release Notes for Safari Technology Preview 240

Mar 26, 2026

by Jon Davis

Safari Technology Preview Release 240 is now available for download for macOS Tahoe and macOS Sequoia. If you already have Safari Technology Preview installed, you can update it in System Settings under General → Software Update.

This release includes WebKit changes between: 308418@main…309286@main.

CSS

New Features

  • Added support for the revert-rule CSS keyword, which rolls back the cascade to behave as if the current style rule had not been present. (308733@main) (171132753)

Resolved Issues

  • Fixed an issue on macOS where custom CSS scrollbars could be cut off and the scrollbar corner rect was sized incorrectly. (309119@main) (168566468)
  • Fixed hanging-punctuation to support U+0027 (apostrophe) and U+0022 (quotation mark) as hangable quotes. (308597@main) (171672576)
  • Fixed hanging-punctuation to allow ideographic space (U+3000) to hang when used with the first value. (308605@main) (171679311)

Editing

Resolved Issues

  • Fixed an issue where the Font Picker style selection became unusable after changing fonts when editing multiple lines of text. (308562@main) (110651645)
  • Fixed an issue where emoji images were not preserved correctly when copying and pasting content across different websites. (309176@main) (162708499)
  • Fixed an issue where text selection would jump unexpectedly when selecting absolutely-positioned content inside an element with user-select: none. (308451@main) (170475401)

Forms

Resolved Issues

  • Fixed an issue where keyboard tabbing position was lost when a focused button became disabled, causing focus to jump to the beginning of the page. (308991@main) (120676409)

HTML

Resolved Issues

  • Fixed viewport <meta> parsing to correctly treat form feed as ASCII whitespace per the HTML specification. (309044@main) (108440799)
  • Fixed incorrect parsing of pixel-length margin attributes on <body>, <iframe>, and <frame> elements. (308526@main) (171240848)

Media

Resolved Issues

  • Fixed an issue where decoding WebM audio files with more than two channels would fail. (308749@main) (82160691)
  • Fixed MediaCapabilities.decodingInfo() incorrectly reporting VP8 in WebM as not supported. (308789@main) (127339546)
  • Fixed an issue where MP4 files containing Opus audio tracks could not be decoded with decodeAudioData. (309140@main) (170196423)
  • Fixed an issue where Live Text selection was unavailable on paused fullscreen videos. (308498@main) (170817667)
  • Fixed an issue where FairPlay-protected VP9 content failed to play via MediaSource. (308622@main) (171210968)
  • Fixed an issue where autoplay would proceed before default text tracks finished loading. (308796@main) (171699293)
  • Fixed the currentTime getter to return defaultPlaybackStartPosition when no media player exists. (308654@main) (171722368)
  • Fixed HTMLMediaElement to fire a timeupdate event when resetting the playback position during media load as required by the specification. (308695@main) (171785463)
  • Fixed an issue where the media player preload attribute was not properly updated when the autoplay attribute was set. (308815@main) (171883159)

PDF

Resolved Issues

  • Fixed an issue where panning a zoomed-in PDF on iOS would frequently rubber band back to the starting position. (309264@main) (156854435)

Rendering

New Features

  • Added support for subpixel inline layout, enabling more precise text and inline element positioning. (309251@main) (171835370)

Resolved Issues

  • Fixed an issue where table cells with rowspan values exceeding the actual number of rows were incorrectly computing heights. (309153@main) (3209126)
  • Fixed an issue where replaced elements with intrinsic content size keywords like fit-content were not properly accounting for aspect ratio constraints. (308995@main) (168264069)
  • Fixed an issue where table sections with explicit heights did not properly constrain and distribute space among contained rows. (308540@main) (169235210)
  • Fixed an issue where auto table layout did not honor max-width on table cells when distributing width between them. (308934@main) (171459245)
  • Fixed an issue where border-spacing incorrectly included collapsed columns in auto table layout calculations. (308549@main) (171468102)
  • Fixed an issue where percentage-height children of table cells with unresolvable percentage heights were not sized intrinsically. (308547@main) (171469500)
  • Fixed an issue where MathML token elements ignored -webkit-text-fill-color when painting math variant glyphs. (308911@main) (172020318)
  • Fixed an issue where cell backgrounds in collapsed-border tables extended into adjacent cells’ border space at table edges. (308969@main) (172068907)
  • Fixed an issue where list item margins were computed incorrectly when the page was zoomed in or out. (309152@main) (172312498)
  • Fixed an issue where about:blank iframes did not always have a transparent background. (309212@main) (172400258)

SVG

Resolved Issues

  • Fixed an issue where the XML document parser did not defer inline script execution until pending stylesheets had loaded. (308980@main) (122574381)
  • Fixed an issue where SVG elements referencing non-existent filter IDs were not rendered. (308809@main) (164046592)
  • Fixed an issue where removeAttribute for width or height on an SVG root element did not reset to the default 300×150 dimensions. (308906@main) (170233990)
  • Fixed an issue where UI events such as wheel failed to fire for inner SVG elements. (309010@main) (171703966)
  • Fixed onbegin, onend, and onrepeat event handler attributes on SVGAnimationElement to properly map to their corresponding event types. (309273@main) (172533070)

Deprecations

  • Removed the non-standard nearestViewportElement and farthestViewportElement properties from SVGGraphicsElement, aligning with the SVG2 specification. (308436@main) (171262197)

Scrolling

Resolved Issues

  • Fixed a scroll snap issue where navigating between items could incorrectly snap back when layout changes occurred. (308420@main) (166596210)
  • Fixed an issue where pages using the Navigation API could have offset hit test locations, making elements unclickable. (308976@main) (171752650)

Web API

New Features

  • Added support for a wider range of characters in DOM element and attribute names, aligning with the updated WHATWG specification. (308884@main) (95205349)

Resolved Issues

  • Fixed location.ancestorOrigins returning stale origins after an iframe is removed from the document. (309126@main) (169097730)

Web Extensions

Resolved Issues

  • Fixed an issue where extensions with a trailing comma in manifest.json failed to load in Safari. (308935@main) (171749937)

Web Inspector

New Features

  • Added support for showing contrast information in the Color Picker when editing background color properties. (308653@main) (171332734)

Resolved Issues

  • Fixed an issue where previewing resources in the Network tab displayed an error upon navigating away and Preserve Log was enabled. (308559@main) (171216835)
  • Fixed an issue where selected DOM node keys in a Map in the Scope Chain sidebar had unreadable white text on a light background. (309006@main) (171840122)

WebAssembly

Resolved Issues

  • Fixed WebAssembly.compileStreaming and WebAssembly.instantiateStreaming to correctly accept compileOptions for JS string builtins. (308234@main, 308419@main) (170989896)