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Apple's opt-in preview channel for upcoming Safari and WebKit features, distributed as periodic builds for macOS to let developers test changes early.
Safari Technology Preview 254 fixes four accessibility bugs and two animation bugs, among them VoiceOver announcing every focused ARIA menu item as selected. Teams carrying workarounds for any of them now have a build to test their removal against.
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Two accessibility name calculation bugs and six animation timeline bugs are resolved in WebKit's latest preview build, including scroll-timeline-name matching across shadow boundaries and a removal of three margin-trim values.
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The new WebKit preview matches style-originated scroll timelines globally, so a declaration no longer has to sit in the animated element's tree. Four of the seven animation entries in the notes settle which timeline a target resolves to.
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Safari's loader took its host hooks from a proposal last updated in January 2016, which is why the top-level await bugs survived years of patching, and why the rewrite only helps traffic already on Safari 27.
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Twelve new CSS features land in the preview, including a detector for at-rules and comma lists in @container. It is still a preview build, so no polyfill comes out on the strength of it.
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