# Safari Technology Preview 52 Release Notes Preview the latest web technology updates including: Legacy NPAPI Plug-ins, Service Worker, Loading, JavaScript, CSS, Web API, Accessibility, Web Driver, Web Inspector, WebAssembly, and Media. ## Overview [Safari Technology Preview](https://webkit.org/blog/6017/introducing-safari-technology-preview/) Release 52 is now [available for download](https://webkit.org/downloads/) for macOS Sierra and macOS High Sierra. If you already have Safari Technology Preview installed, you can update from the Mac App Store’s Updates tab. This release covers WebKit revisions [228856-229535](https://trac.webkit.org/log?stop_rev=228856&rev=229535&limit=999). ### Legacy NPAPI Plug-ins - Removed support for running legacy NPAPI plug-ins other than Adobe Flash ### Service Worker - Changed Fetch event release assert to take into account the fetch mode ([r228930](https://trac.webkit.org/changeset/228930/webkit/)) - Changed to not use a Service Worker in the case of document redirection if it will be already served by AppCache ([r229086](https://trac.webkit.org/changeset/229086/webkit/)) - Fix loads for a Document controlled by a Service Worker to not use AppCache ([r229181](https://trac.webkit.org/changeset/229181/webkit/)) - Updated Service Worker to respect IndexedDB and DOM cache partitioning ([r229483](https://trac.webkit.org/changeset/229483/webkit/)) ### Loading - Added support for `preconnect` link headers ([r229308](https://trac.webkit.org/changeset/229308/webkit/)) - Fixed converting a load to a download to work with async policy delegates ([r229177](https://trac.webkit.org/changeset/229177/webkit/)) - Prevented DNS prefetching from being re-enabled ([r229061](https://trac.webkit.org/changeset/229061/webkit/)) ### JavaScript - Fixed handling undefined global variables with the same name as an element ID ([r229451](https://trac.webkit.org/changeset/229451/webkit/)) - Made `Number.isInteger` an intrinsic ([r228968](https://trac.webkit.org/changeset/228968/webkit/)) ### CSS - Added new CSS `env()` constants for use with fullscreen ([r229475](https://trac.webkit.org/changeset/229475/webkit/)) - Fixed `::selection` CSS `stroke-color` and `stroke-width` to be applied to selected text in text fields ([r229147](https://trac.webkit.org/changeset/229147/webkit/)) ### Web API - Fixed HTML `pattern` attribute to set `u` flag for regular expressions ([r229363](https://trac.webkit.org/changeset/229363/webkit/)) - Fixed `replaceState` causing back and forward navigation problems on a page with `` ([r229375](https://trac.webkit.org/changeset/229375/webkit/)) - Fixed `document.open` to cancel navigation policy check in addition to cancelling the existing provisional load ([r228922](https://trac.webkit.org/changeset/228922/webkit/)) ### Accessibility - Added more accessibility events support ([r229310](https://trac.webkit.org/changeset/229310/webkit/)) - Dispatched `accessiblesetvalue` event ([r229112](https://trac.webkit.org/changeset/229112/webkit/)) - Fixed keyboard focus to follow the VoiceOver cursor into web content or within web content ([r228857](https://trac.webkit.org/changeset/228857/webkit/)) - Fixed WebKit running spell checker even on non-editable content text ([r229500](https://trac.webkit.org/changeset/229500/webkit/)) ### Web Driver - Fixed clicking on a disabled option element to not produce an error ([r229212](https://trac.webkit.org/changeset/229212/webkit/)) - Fixed stale elements not getting detected when removed from the DOM ([r229210](https://trac.webkit.org/changeset/229210/webkit/)) - Fixed failed provisional loads causing “Navigate To” command to hang ([r228887](https://trac.webkit.org/changeset/228887/webkit/)) - Fixed script evaluations via WebDriver to have a user gesture indicator ([r229206](https://trac.webkit.org/changeset/229206/webkit/)) ### Web Inspector - Changed Canvas Tab to scroll into view and inspect an element if Canvas has a DOM node ([r229044](https://trac.webkit.org/changeset/229044/webkit/)) ### WebAssembly - Added cache for memory address and size on an instance ([r228966](https://trac.webkit.org/changeset/228966/webkit/)) ### Media - Fixed the `webkitfullscreenchange` event to fire at the same time as `:-webkit-full-screen` pseudo selector changes ([r229466](https://trac.webkit.org/changeset/229466/webkit/), [r229487](https://trac.webkit.org/changeset/229487/webkit/)) ### Bug Fix - Fixed copying a table from the Numbers app and pasting into iCloud Numbers ([r229503](https://trac.webkit.org/changeset/229503/webkit/)) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)