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WebKitJon Davis3 min readrelease notesintro

Release Notes for Safari Technology Preview 250

Read on webkit.org

Summary

Safari Technology Preview 250 ships a batch of web‑platform updates, including new JavaScript resource‑management syntax, several CSS properties, streaming fetch bodies, and WebAssembly SIMD extensions. It also fixes a range of accessibility, rendering, and networking bugs.

  • Adds JavaScript Explicit Resource Management support: `using`, `await using`, `Symbol.dispose`, `DisposableStack`, and `AsyncDisposableStack`.
  • Introduces new CSS features: `ruby-overhang: spaces`, `text-decoration-inset`, `white-space-trim`, `wrap-inside`, and `content` on `::marker`.
  • Fetch API can now upload a `ReadableStream` body and requires the `duplex` request option.
  • WebAssembly gains relaxed SIMD instructions and the ability to define multiple memories in a module.

Front‑end engineers should care because these previewed APIs and CSS properties will soon affect production code and compatibility testing.

6/10
networkingjavascriptcssaccessibilitywebassemblysafari

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