Release Notes for Safari Technology Preview 238

Source: WebKit Blog

Safari Technology Preview Release 238 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 → General → Software Update.

This release includes WebKit changes between 306596@main…307618@main:
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Animations

New Features

• Enabled threaded time‑based animation resolution, synchronizing accelerated time‑based animations with scroll‑driven animations while preserving performance by running animations off the main thread. This also allows CSS Motion Path animations to be accelerated. (307252@main) (170131323)

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CSS

New Features

• Added support for the CSS :open pseudo‑class, which matches form elements and other elements in an open state. (307295@main) (170108337)

Resolved Issues

• Fixed scrollable overflow computation for block containers to account for padding-inline-end, aligning with the CSS Overflow specification. (307212@main) (144312078)
• Fixed rendering of linear gradients when all color stops are at the same position. (306823@main) (169063497)

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Editing

New Features

• Added menu items to convert editable text between Simplified and Traditional Chinese characters in the Transformations submenu. (306761@main) (156354464)

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Forms

New Features

• Enabled the customizable element, allowing custom styling and content in dropdowns using appearance: base-select. (307548@main) (170328089)

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Networking

Resolved Issues

• Fixed an issue where Safari’s address bar could display an internationalized domain name (IDN) homograph as a visually identical legitimate Latin domain, enabling potential phishing attacks. (307005@main) (166796168)
• Fixed incorrect URL query percent‑encoding when using non‑UTF‑8 character encodings such as iso‑8859‑2, windows‑1250, and gbk. (306768@main) (169566553)

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Rendering

Resolved Issues

• Fixed a performance issue causing a hang when rendering tables with a large number of rowspan="0" cells. (306891@main) (146056348)

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SVG

Resolved Issues

• Updated the default values of fx and fy attributes on SVGRadialGradientElement to 50 % to align with the SVG 2 specification. (306811@main) (169645572)
• Fixed SVGAnimatedRect.baseVal to ignore invalid values set on the viewBox attribute (e.g., negative width or height), aligning with Firefox and Chrome. (307463@main) (170214971)
• Fixed SVG length attributes to reset to their default values when removed, rather than retaining previously set values. (307585@main) (170360351)

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Scrolling

New Features

• Enabled scroll anchoring, which prevents visible jumps in scroll position when content is inserted or removed above the viewport. (307475@main) (170279026)

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Web API

New Features

• Added support for ReadableStream.from() to create a ReadableStream from an async iterable or iterable. (306786@main) (169605740)
• Added support for transferring ReadableStream objects via postMessage(). (307068@main) (169950592)

Resolved Issues

• Fixed an issue where Speculation Rules did not trigger prefetches for anchor elements that were not themselves visible but had visible descendants. (306730@main) (169561588)
• Fixed NavigateEvent.canIntercept to correctly return false when navigating to a URL with a different port, aligning with the Navigation API specification. (307316@main) (169845691)

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Web Inspector

New Features

• Improved discoverability of color formats and gamuts in the color picker by adding explicit format and gamut toggle controls. (306691@main) (168216591)

Resolved Issues

• Fixed an issue where the text filter in the Sources tab did not apply to Local Overrides and Console Snippets sections. (306647@main) (169443917)
• Fixed an issue where tree outlines in Web Inspector would intermittently show blank content while scrolling when a filter was active. (306680@main) (169502061)
• Fixed an issue in the Timelines tab where rows containing object previews were sometimes not visible in the heap snapshot data grid. (307358@main) (170164522)
• Fixed context‑menu items in the Elements tab to only display relevant options when multiple DOM nodes are selected. (307485@main) (170307979)

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WebAssembly

New Features

• Added support for JavaScript Promise Integration (JSPI) for WebAssembly, enabling WebAssembly code to suspend and resume execution while waiting for JavaScript promises. (307404@main) (170260385)

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WebRTC

Resolved Issues

• Fixed RTCRtpSynchronizationSource.timestamp to use the correct time base, aligning with the WebRTC specification. (307063@main) (1)

- Fixed `RTCIceCandidate.toJSON()` to include the `usernameFragment` field in the serialized output.  
  ([306845@main](https://commits.webkit.org/306845@main))  (169679947)

- Fixed `RTCRtpTransceiver.setCodecPreferences()` to accept codec entries regardless of the `mimeType` case, aligning with Firefox and the specification.  
  ([307062@main](https://commits.webkit.org/307062@main))  (169789074)

- Fixed `RTCRtpSender` to allow a `maxFramerate` encoding parameter value of `0`, aligning with the specification and other browsers.  
  ([307034@main](https://commits.webkit.org/307034@main))  (169863687)