# Safari Technology Preview 28 Release Notes
Preview the latest web technology updates including: Power and Performance, CSS, JavaScript, Web API, Web Inspector, WebDriver, Accessibility, Media, Rendering, WebCrypto, Security, and AppleScript.
## Overview
[Safari Technology Preview](https://webkit.org/blog/6017/introducing-safari-technology-preview/) Release 28 is now [available for download](https://webkit.org/downloads/) for macOS 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 [214535-215271](https://trac.webkit.org/log?stop_rev=214535&rev=215271&limit=280).
### Power and Performance
- Changed to pause silent WebAudio rendering in background tabs ([r214721](https://trac.webkit.org/changeset/214721))
- Changed to pause animated SVG images on pages loaded in the background ([r214561](https://trac.webkit.org/changeset/214561))
- Changed to make inaudible background tabs become eligible for memory kill after 8 minutes ([r215077](https://trac.webkit.org/changeset/215077))
- Changed to kill any WebContent process using over 16 GB of memory ([r215055](https://trac.webkit.org/changeset/215055))
- Throttled DOM Timers to 30fps in cross-origin `iframes` that the user did not interact with ([r215116](https://trac.webkit.org/changeset/215116))
- Throttled `requestAnimationFrame` callbacks to 30fps in cross-origin `iframes` the user did not interact with ([r215070](https://trac.webkit.org/changeset/215070), [r215153](http://trac.webkit.org/r215153))
### CSS
- Adapted `content-alignment` properties to the new baseline syntax ([r214624](https://trac.webkit.org/changeset/214624))
- Adapted `place-content` alignment shorthand to the new baseline syntax ([r214852](https://trac.webkit.org/changeset/214852))
- Adapted `self-alignment` properties to the new baseline syntax ([r214564](https://trac.webkit.org/changeset/214564))
- Fixed scroll offset jumps after a programmatic scroll in an overflow container with scroll snapping ([r215075](https://trac.webkit.org/changeset/215075))
- Implemented the `place-items` shorthand ([r214966](https://trac.webkit.org/changeset/214966))
- Implemented `stroke-color` CSS property ([r215261](https://trac.webkit.org/changeset/215261))
- Implemented `stroke-miterlimit` CSS property ([r214787](https://trac.webkit.org/changeset/214787))
- Unprefixed CSS cursor values `grab` and `grabbing` ([r215146](https://trac.webkit.org/changeset/215146))
### JavaScript
- Fixed objects with gaps between numerical keys getting filled by `NaN` values ([r214714](https://trac.webkit.org/changeset/214714))
- Fixed `Object.seal()` and `Object.freeze()` on global `this` ([r215072](https://trac.webkit.org/changeset/215072))
- Fixed `String.prototype.replace` to correctly apply special replacement parameters when passed a function ([r214662](https://trac.webkit.org/changeset/214662))
### Web API
- Changed `_blank`, `_self`, `_parent`, and `_top` browsing context names to be case-insensitive ([r214944](https://trac.webkit.org/changeset/214944))
- Cleaned up touch event handler registration when moving nodes between documents ([r214819](https://trac.webkit.org/changeset/214819))
- Fixed `` to prevent breaking all mouse events when changing to disabled while active ([r214955](https://trac.webkit.org/changeset/214955))
- Prevented double downloads of preloaded content from when the content is in MemoryCache ([r215229](https://trac.webkit.org/changeset/215229))
- Fixed WebSocket.send ([r215102](https://trac.webkit.org/changeset/215102/webkit))
### Web Inspector
- Added a preference for Auto Showing Scope Chain sidebar on pause ([r214847](https://trac.webkit.org/changeset/214847))
- Changed the order of Debugger tab sidebar panels: Scope Chain, Resource, Probes ([r215047](https://trac.webkit.org/changeset/215047))
- Changed XHR breakpoints to be global ([r214956](https://trac.webkit.org/changeset/214956))
- Changed hierarchical path component labels to guess directionality based on content for RTL layout ([r214862](https://trac.webkit.org/changeset/214862))
- Fixed RTL alignment of close button shown while docked ([r214902](https://trac.webkit.org/changeset/214902))
- Fixed RTL layout issues in call frame tree elements and async call stacks ([r214846](https://trac.webkit.org/changeset/214846))
- Fixed RTL layout issues in the debugger dashboard putting arrows on the wrong side ([r214899](https://trac.webkit.org/changeset/214899))
- Fixed RTL layout issues in Type Profiler popovers ([r214906](https://trac.webkit.org/changeset/214906))
- Fixed misplaced highlights in Search results of the Search navigation sidebar for RTL layout ([r214864](https://trac.webkit.org/changeset/214864))
- Fixed disappearing section when clicking on the body of a CSS rule after editing ([r214863](https://trac.webkit.org/changeset/214863))
- Fixed showing indicators for hidden DOM element breakpoints in the Elements tab ([r214844](https://trac.webkit.org/changeset/214844))
- Fixed blank Network tab content view after reload ([r214551](https://trac.webkit.org/changeset/214551))
- Made “Enter Class Name” text field wider so the placeholder text doesn’t clip ([r215192](https://trac.webkit.org/changeset/215192))
- Fixed probe values not showing in the Debugger tab sidebar ([r214967](https://trac.webkit.org/changeset/214967))
- Fixed focusing the Find banner immediately after showing it ([r214856](https://trac.webkit.org/changeset/214856))
- Fixed showing Source Map Resources in the Debugger Sources list ([r215082](https://trac.webkit.org/changeset/215082))
- Fixed Styles sidebar warning icon appearing inside property value text ([r214617](https://trac.webkit.org/changeset/214617))
- Fixed broken tabbing in Styles sidebar when additional “:” and “;” are in the property value ([r215170](https://trac.webkit.org/changeset/215170))
- Fixed clipped data in WebSockets data grid ([r215206](https://trac.webkit.org/changeset/215206))
- Fixed staying scrolled to the bottom as new WebSocket log messages get added ([r214587](https://trac.webkit.org/changeset/214587))
- Included additional pause reason details for DOM “subtree modified” breakpoint ([r214861](https://trac.webkit.org/changeset/214861))
- Included more Network information in Resource Details Sidebar ([r214903](https://trac.webkit.org/changeset/214903))
- Included all headers in the Request Headers section of the Resource details sidebar ([r215062](https://trac.webkit.org/changeset/215062))
### WebDriver
- Fixed an issue that prevented non-popup windows from being maximized or resized
- Fixed an issue that caused previously opened tabs to reopen when Safari was launched in order to run a WebDriver test
### Accessibility
- Exposed a new AXSubrole for the explicit ARIA “group” role ([r214623](https://trac.webkit.org/changeset/214623))
- Fixed VoiceOver web article navigation with an article rotor for sites like Facebook and Twitter ([r215236](https://trac.webkit.org/changeset/215236))
### Media
- Fixed seeks to `currentTime=0` if `currentTime` is already `0` ([r214959](https://trac.webkit.org/changeset/214959))
### Rendering
- Fixed clipping across page breaks when including `