Safari Technology Preview 238 Released with WebKit Updates

Safari Technology Preview serves as a proving ground for features that will eventually land in the main Safari browser, offering a more stable and curated experience than the daily WebKit Nightly builds. Unlike the Nightly builds, the Technology Preview is signed by Apple and integrates with iCloud features like keychain and tab syncing, making it a practical daily driver for developers. Updates are typically released every two weeks, providing a steady stream of new web technologies to test. This release enables threaded time-based animation resolution, a significant step towards smoother on-screen motion. This allows accelerated, time-based animations to synchronize with scroll-driven animations by running them off the main thread, which also enables the acceleration of CSS Motion Path animations. For developers, this means more complex, performant animations that remain responsive to user interaction without bogging down the main thread. Developers also gain more styling control with support for the CSS `:open` pseudo-class and customizable `<select>` elements. The `:open` pseudo-class allows for styling elements like `<details>` and `<dialog>` when they are in an open state, while the customizable `<select>` element provides the ability to apply custom styles to dropdowns using `appearance: base-select`. On the security front, this update addresses a critical vulnerability involving internationalized domain name (IDN) homographs. The fix prevents a potential phishing attack where a malicious domain could be displayed as a visually identical but legitimate Latin domain in the address bar. The performance improvements to WebKit's JavaScript engine have direct implications for both web and native iOS/macOS applications. Since WKWebView, the framework for displaying web content in native apps, uses the same Nitro JavaScript engine as Safari, these optimizations translate to faster performance for hybrid apps and in-app web views. All browsers on iOS are also required to use the WebKit engine. This release of Safari Technology Preview is compatible with macOS Tahoe and macOS Sequoia. The continuous evolution of WebKit, showcased in these previews, directly influences the capabilities and standards compliance of Safari across all of Apple's platforms, including iOS, iPadOS, and visionOS.