--- title: Release Notes for Safari Technology Preview 250 | daily.dev description: Safari Technology Preview 250 is available for macOS Golden Gate and macOS Tahoe, covering WebKit changes between build 317507 and 317934. Highlights include... canonical: https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Release Notes for Safari Technology Preview 250 | daily.dev og:description: Safari Technology Preview 250 is available for macOS Golden Gate and macOS Tahoe, covering WebKit changes between build 317507 and 317934. Highlights include... og:url: https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy og:image: https://api.daily.dev/og/posts/q085bH1QY.png og:image:alt: Release Notes for Safari Technology Preview 250 og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Release Notes for Safari Technology Preview 250 **[WebKit](https://daily.dev/sources/webkit)** · 4 min read · 5 upvotes · 2 comments ## Summary Safari Technology Preview 250 is available for macOS Golden Gate and macOS Tahoe, covering WebKit changes between build 317507 and 317934. Highlights include new CSS properties (ruby-overhang: spaces, ::marker content, text-decoration-inset, white-space-trim, wrap-inside), removal of the non-standard CSS text color value in favor of canvastext, JavaScript support for Explicit Resource Management (using/await using, Symbol.dispose, DisposableStack) and Iterator.zip(), initial fetch() support for uploading ReadableStream bodies with a new duplex option on Request, WebAssembly relaxed SIMD and multiple memories support, plus numerous accessibility, scrolling, media, storage, and Web Inspector bug fixes. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What new CSS properties does Safari Technology Preview 250 support? Safari Technology Preview 250 adds support for the spaces value of ruby-overhang (with none now an alias for spaces), the content property on the ::marker pseudo-element, text-decoration-inset, white-space-trim, and wrap-inside. It also removes the non-standard text color value, recommending canvastext as the replacement. _Track new CSS capabilities like these on daily.dev before they land in stable Safari._ ### Does Safari support the JavaScript Explicit Resource Management proposal with using and await using? Yes, Safari Technology Preview 250 adds support for the Explicit Resource Management proposal, including using and await using declarations, Symbol.dispose, DisposableStack, and AsyncDisposableStack. It also adds Iterator.zip() and Iterator.zipKeyed() from the Joint Iteration proposal. _Developers adopting new JS resource-management syntax follow engine support updates like this on daily.dev._ ### Can fetch() upload a ReadableStream request body in Safari Technology Preview? Safari Technology Preview 250 adds initial support for uploading a ReadableStream body with fetch(), along with the duplex option on Request, which is required when uploading a streamed body. This enables streaming request bodies rather than only streaming responses. _Follow fetch() streaming support progress on daily.dev when building cross-browser networking code._ ## Community discussion Top comments from developers on daily.dev. **@allinonetools** · 1 upvotes > Interesting update, especially the `using`/`await using` support and ReadableStream uploads. Safari keeps quietly closing some important gaps for modern web development. **@agustinbarrientos** · 0 upvotes > Do the streaming upload tests cover a mid-body abort and verify that the following request still succeeds? ## Similar posts on daily.dev - [Release Notes for Safari Technology Preview 251](https://daily.dev/posts/release-notes-for-safari-technology-preview-251-qokmenlla) · WebKit · 3 upvotes · 0 comments - [News from WWDC26: WebKit in Safari 27 beta](https://daily.dev/posts/news-from-wwdc26-webkit-in-safari-27-beta-cz81svuy5) · WebKit · 12 upvotes · 1 comments - [New to the web platform in November](https://daily.dev/posts/new-to-the-web-platform-in-november-hl3ileus2) · web.dev · 2 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript), [#css](https://daily.dev/tags/css), [#webassembly](https://daily.dev/tags/webassembly), [#safari](https://daily.dev/tags/safari) [View this post on daily.dev](https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Release Notes for Safari Technology Preview 250","url":"https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy"},"datePublished":"2026-08-13T21:34:37.618Z","dateModified":"2026-09-13T20:58:09.740Z","description":"Safari Technology Preview 250 is available for macOS Golden Gate and macOS Tahoe, covering WebKit changes between build 317507 and 317934. 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Safari keeps quietly closing some important gaps for modern web development.","datePublished":"2026-08-15T03:19:27.328Z","url":"https://daily.dev/posts/q085bH1QY#c-khNZfV5F9","author":{"@type":"Person","name":"AllInOneTools","url":"https://daily.dev/allinonetools","image":"https://media.daily.dev/image/upload/s--4ZT8QlF0--/f_auto/v1769790028/avatars/avatar_igzBsWloJeaegzm9bQltZ?_a=BAMAMiiu0"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1}},{"@type":"Comment","text":"Do the streaming upload tests cover a mid-body abort and verify that the following request still succeeds?","datePublished":"2026-08-15T17:23:31.541Z","url":"https://daily.dev/posts/q085bH1QY#c-7SxJfwOpZ","author":{"@type":"Person","name":"Agustin Barrientos","url":"https://daily.dev/agustinbarrientos","image":"https://media.daily.dev/image/upload/s--5ayxQnqn--/f_auto/v1788281802/avatars/avatar_wQYYVe5Tbj0NJ7C7qPoa8?_a=BAMAMicg0"}}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/release-notes-for-safari-technology-preview-250-q085bh1qy#faq","mainEntity":[{"@type":"Question","name":"What new CSS properties does Safari Technology Preview 250 support?","acceptedAnswer":{"@type":"Answer","text":"Safari Technology Preview 250 adds support for the spaces value of ruby-overhang (with none now an alias for spaces), the content property on the ::marker pseudo-element, text-decoration-inset, white-space-trim, and wrap-inside. It also removes the non-standard text color value, recommending canvastext as the replacement. Track new CSS capabilities like these on daily.dev before they land in stable Safari."}},{"@type":"Question","name":"Does Safari support the JavaScript Explicit Resource Management proposal with using and await using?","acceptedAnswer":{"@type":"Answer","text":"Yes, Safari Technology Preview 250 adds support for the Explicit Resource Management proposal, including using and await using declarations, Symbol.dispose, DisposableStack, and AsyncDisposableStack. It also adds Iterator.zip() and Iterator.zipKeyed() from the Joint Iteration proposal. Developers adopting new JS resource-management syntax follow engine support updates like this on daily.dev."}},{"@type":"Question","name":"Can fetch() upload a ReadableStream request body in Safari Technology Preview?","acceptedAnswer":{"@type":"Answer","text":"Safari Technology Preview 250 adds initial support for uploading a ReadableStream body with fetch(), along with the duplex option on Request, which is required when uploading a streamed body. This enables streaming request bodies rather than only streaming responses. Follow fetch() streaming support progress on daily.dev when building cross-browser networking code."}}]} ```