# Safari Technology Preview 138 Release Notes Preview the latest web technology updates including: Web Inspector, CSS, Experimental Model Element, Media, Web Animations, WebAuthn, SVG, Web API, Service Workers, WebRTC, WebAssembly, Web Extensions, and Bug Fixes. ## Overview [Safari Technology Preview](https://webkit.org/blog/6017/introducing-safari-technology-preview/) Release 138 is now [available for download](https://webkit.org/downloads/) for macOS Big Sur and macOS Monterey. If you already have Safari Technology Preview installed, you can update in the Software Update pane of System Preferences on macOS. This release covers WebKit revisions [286534-286944](https://trac.webkit.org/log?stop_rev=286534&rev=286944&limit=410). **Note:** Tab Groups do not sync in this release. ### Web Inspector - Elements Tab - Added support for Cascade Layers in the Styles sidebar ([r286558](https://trac.webkit.org/changeset/286558/webkit/)) - Added a swatch for `align-items` and `align-self` ([r286875](https://trac.webkit.org/changeset/286875/webkit/)) - Added a swatch for `justify-content`, `justify-items`, and `justify-self` ([r286885](https://trac.webkit.org/changeset/286885/webkit/)) - Added CSS variable names to property name completion list ([r286890](https://trac.webkit.org/changeset/286890/webkit/)) - Added an option to group CSS variables by value type in the Computed sidebar ([r286876](https://trac.webkit.org/changeset/286876/webkit/)) - Enabled fuzzy matching for CSS completions in the Styles sidebar ([r286792](https://trac.webkit.org/changeset/286792/webkit/), [r286611](https://trac.webkit.org/changeset/286611/webkit/)) ### CSS - Enabled `:focus-visible` pseudo-class by default ([r286783](https://trac.webkit.org/changeset/286783/webkit/), [r286776](https://trac.webkit.org/changeset/286776/webkit/), [r286775](https://trac.webkit.org/changeset/286775/webkit/)) - Enabled the `resolution` media query by default ([r286874](https://trac.webkit.org/changeset/286874/webkit/)) - Enabled the CSS Contain property by default ([r286828](https://trac.webkit.org/changeset/286828/webkit/)) - Changed to account for captions when flexing tables with specified sizes ([r286593](https://trac.webkit.org/changeset/286593/webkit/)) - Fixed `perspective()` less than or equal to `1px` to be clamped to `1px` ([r286591](https://trac.webkit.org/changeset/286591/webkit/)) - Fixed `gap` to work correctly when `flex-direction: column-reverse` is applied ([r286654](https://trac.webkit.org/changeset/286654/webkit/)) - Fixed the serialization of `CSSImportRule` ([r286668](https://trac.webkit.org/changeset/286668/webkit/)) - Unprefixed `-webkit-mask` ([r286795](https://trac.webkit.org/changeset/286795/webkit/)) - Unprefixed CSS value `text-align: -webkit-match-parent` ([r286803](https://trac.webkit.org/changeset/286803/webkit/)) - Updated `color-mix()` to support `srgb-linear` and alpha premultiplication ([r286568](https://trac.webkit.org/changeset/286568/webkit/)) ### Experimental Model Element - Added load and error events to distinguish resource load from model readiness ([r286836](https://trac.webkit.org/changeset/286836/webkit/)) ### Media - Fixed various issues with complicated rendering of VTT cues ([r286743](https://trac.webkit.org/changeset/286743/webkit/)) ### Web Animations - Added a way to run scripted animations via `CustomEffect` ([r286555](https://trac.webkit.org/changeset/286555/webkit/)) - Exposed a `frameRate` property to Web Animations ([r286915](https://trac.webkit.org/changeset/286915/webkit/)) ### WebAuthn - Improved WebAuthn Level 2 standards compliance by supporting the `displayName` ([r286746](https://trac.webkit.org/changeset/286746/webkit/)) ### SVG - Fixed `transform-origin` on SVG elements to take into account the transform reference box origin ([r286942](https://trac.webkit.org/changeset/286942/webkit/)) ### Web API - Changed to group radio buttons with no form owner ([r286855](https://trac.webkit.org/changeset/286855/webkit/)) - Fixed the range of `` to be reversible ([r286581](https://trac.webkit.org/changeset/286581/webkit/)) - Fixed an `` that’s been autofilled with obscured content to still be editable ([r286814](https://trac.webkit.org/changeset/286814/webkit/)) - Implemented `AbortSignal.throwIfAborted` ([r286904](https://trac.webkit.org/changeset/286904/webkit/)) - Improved `` value parsing and sanitization ([r286869](https://trac.webkit.org/changeset/286869/webkit/)) - Restored `navigator.hardwareConcurrency` ([r286550](https://trac.webkit.org/changeset/286550/webkit/)) - Fixed setting `onselectionchange` content attribute to add an event listener ([r286898](https://trac.webkit.org/changeset/286898/webkit/)) ### Service Workers - Enabled NavigationPreloadManager by default ([r286540](https://trac.webkit.org/changeset/286540/webkit/)) - Added support for ServiceWorker downloads ([r286944](https://trac.webkit.org/changeset/286944/webkit/)) - Fixed “no-cache” network error ([r286655](https://trac.webkit.org/changeset/286655/webkit/)) - Fixed same-site lax cookies not sent by fetch event handler after page reload ([r286656](https://trac.webkit.org/changeset/286656/webkit/)) ### WebRTC - Closed WebRTC allocation sequence shared socket in case of sequence network failure ([r286539](https://trac.webkit.org/changeset/286539/webkit/)) ### WebAssembly - Added preparation of `WebAssembly.Memory` imports in Wasm/ESM modules ([r286703](https://trac.webkit.org/changeset/286703/webkit/)) ### Web Extensions - Added support for changed `web_accessible_resources` declaration with `manifest_version` 3 - Fixed `runtime.onMessage` listeners not supporting `Promise` returns for the reply message - Show error messages for incorrect match patterns in `web_accessible_resources` - Show error message to `devtools` tabs in Web Inspector when inspecting unsupported targets - Show error message when the service worker background script fails to load ### Bug Fixes - Fixed an issue introduced in Safari Technology Preview 137 where pop-up windows wouldn’t open --- Copyright © 2026 Apple Inc. 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