# Safari Technology Preview 3 Release Notes Preview the latest web technology updates including: JavaScript, CSS, Web APIs, Web Inspector, Rendering, Security, Networking, and Accessibility. ## Overview [Safari Technology Preview](/blog/6017/introducing-safari-technology-preview/) Release 3 is now available for [download](https://developer.apple.com/safari/download/). If you already have Safari Technology Preview installed, you can update from the [Mac App Store’s Updates tab](macappstore://showUpdatesPage). Release 3 of Safari Technology Preview covers WebKit revisions [199086–199865](https://trac.webkit.org/log?action=follow_copy&mode=follow_copy&rev=199865&stop_rev=199086&limit=999). ### JavaScript - Added support for `Symbol.isConcatSpreadable` per the ES6 spec ([r199397](https://trac.webkit.org/changeset/199397)) - Made `RegExp` constructor get the `Symbol.match` property to decide if an object should be constructed like a `RegExp` object per the ES6 spec ([r199106](https://trac.webkit.org/changeset/199106)) - Changed `String.match` and `String.search` to use `RegExp` constructor per the ES6 spec ([r199144](https://trac.webkit.org/changeset/199144)) - Corrected how function declarations are hoisted per the ES6 spec ([r199179](https://trac.webkit.org/changeset/199179)) - Improved parsing of ES6 arrow functions ([r199352](https://trac.webkit.org/changeset/199352)) - Added `RegExp.prototype[@@split]` and made `String.prototype.split` use it per the ES6 spec ([r199731](https://trac.webkit.org/changeset/199731)) - Added `RegExp.prototype[@@search]` ([r199748](https://trac.webkit.org/changeset/199748)) - Updated the treatment of invoking methods on `RegExp.prototype` per the ES6 spec ([r199545](https://trac.webkit.org/changeset/199545)) - Made more test cases pass with ES6 `RegExp` unicode flag ([r199523](https://trac.webkit.org/changeset/199523)) - Added support for caching accesses to `arguments.length` for a performance speed-up ([r199240](https://trac.webkit.org/changeset/199240)) - Corrected the behavior of `throw()` for generators yielding to an inner generator per draft ECMAScript spec ([r199652](https://trac.webkit.org/changeset/199652)) ### CSS - Implemented the functional `:host()` pseudo class ([r199291](https://trac.webkit.org/changeset/199291)) - Improved support for SVG cursor images ([r199625](https://trac.webkit.org/changeset/199625)) - Started using OpenType math fonts by default for MathML ([r199773](https://trac.webkit.org/changeset/199773)) - Fixed measurement of hanging punctuation ([r199777](https://trac.webkit.org/changeset/199777)) - Improved hyphenation when the last line in a paragraph only contains one syllable of a word ([r199818](https://trac.webkit.org/changeset/199818)) - Fixed a layout problem affecting CSS Grid items without a static inline position in RTL languages ([r199098](https://trac.webkit.org/changeset/199098)) - Fixed positioned items with gaps for CSS Grid ([r199223](https://trac.webkit.org/changeset/199223)) - Added support for CSS Grid `grid-template-columns` `repeat(auto-fill, …)` and `repeat(auto-fit, …)` ([r199343](https://trac.webkit.org/changeset/199343)) - Fixed positioned items with content alignment in CSS Grids ([r199657](https://trac.webkit.org/changeset/199657)) - Started using `grid-template-areas` to determine the explicit grid ([r199661](https://trac.webkit.org/changeset/199661)) - Corrected CSS Grid layout by using the margin box for non-auto minimum sizes ([r199728](https://trac.webkit.org/changeset/199728)) ### Web APIs - Added support setting and retrieving `Blob` values in IndexedDB ([r199120](https://trac.webkit.org/changeset/199120), [r199230](https://trac.webkit.org/changeset/199230), [r199499](https://trac.webkit.org/changeset/199499), [r199524](https://trac.webkit.org/changeset/199524), [r199708](https://trac.webkit.org/changeset/199708), [r199730](https://trac.webkit.org/changeset/199730)) - Corrected `MessageEvent.source` result once `window` has been fully created ([r199087](https://trac.webkit.org/changeset/199087)) - Improved stability when the first child of a shadow root is a comment node ([r199097](https://trac.webkit.org/changeset/199097)) - Made `CSS` be a proper constructor on the `window` object with static functions ([r199112](https://trac.webkit.org/changeset/199112)) - Exposed the `Crypto` constructor on the `window` object ([r199159](https://trac.webkit.org/changeset/199159)) - Added support for `display: contents` on `` elements ([r199151](https://trac.webkit.org/changeset/199151)) - Fixed `FontFace` so it will be properly reject the returned promise if Content Security Policy blocks all the URLs ([r199611](https://trac.webkit.org/changeset/199611)) - Made `FontFaceSet` handle null correctly ([r199216](https://trac.webkit.org/changeset/199216)) - Corrected `DOMTokenList.contains()` so it does not throw an exception ([r199296](https://trac.webkit.org/changeset/199296)) - Made `Selection.deleteFromDocument` not delete a character when the selection is a caret per the spec ([r199585](https://trac.webkit.org/changeset/199585)) - Improved the IndexedDB bindings to better match the spec ([r199750](https://trac.webkit.org/changeset/199750), [r199774](https://trac.webkit.org/changeset/199774)) - Made `AudioBufferSourceNode.buffer` nullable ([r199751](https://trac.webkit.org/changeset/199751)) - Improved stability handling a wheel event that closes a frame ([r199181](https://trac.webkit.org/changeset/199181)) ### Web Inspector - Made it possible to expand objects in the Instances heap snapshot view to see what it retains ([r199379](https://trac.webkit.org/changeset/199379)) - Improved performance dramatically in the Timelines tab when recording pages with a lot of rapid activity and for long recordings ([r199747](https://trac.webkit.org/changeset/199747)) - Improved JavaScript pretty printing performance by using Esprima and by no longer blocking the main thread ([r199168](https://trac.webkit.org/changeset/199168), [r199169](https://trac.webkit.org/changeset/199169)) - Improved the profiler’s sampling rate to get closer to a 1ms sample frequency ([r199092](https://trac.webkit.org/changeset/199092)) - Improved filtering in Open Quickly dialog ([r199143](https://trac.webkit.org/changeset/199143), [r199226](https://trac.webkit.org/changeset/199226)) - Made the Open Quickly dialog keep its resource list up to date ([r199207](https://trac.webkit.org/changeset/199207)) - Stopped trying to match color patterns in JavaScript source code to improve performance of large resources ([r199095](https://trac.webkit.org/changeset/199095)) - Changed take snapshot navigation button to a camera glyph ([r199177](https://trac.webkit.org/changeset/199177)) - Corrected source code location links in the JavaScript profile Call Trees view ([r199201](https://trac.webkit.org/changeset/199201)) - Made XHRs and Web Workers full-text searchable ([r199263](https://trac.webkit.org/changeset/199263)) - Improved the appearance of DOM nodes in object previews ([r199322](https://trac.webkit.org/changeset/199322)) - Improved the tab bar rendering when the tabs are small ([r199325](https://trac.webkit.org/changeset/199325)) - Corrected dock controls disappearing from the toolbar after leaving fullscreen ([r199395](https://trac.webkit.org/changeset/199395)) - Started remembering the zoom factor as a persistent setting across sessions ([r199396](https://trac.webkit.org/changeset/199396)) - Corrected `sourceMappingURL` not being used when `sourceURL` was also set ([r199688](https://trac.webkit.org/changeset/199688)) - Started localizing sizes and times by using `Number.prototype.toLocaleString` ([r199635](https://trac.webkit.org/changeset/199635)) - Made `sourceMappingURL` work more reliably across reloads ([r199852](https://trac.webkit.org/changeset/199852)) ### Rendering - Improved the time to display for some pages — allowing a short page header to render immediately before other content populates later ([r199155](https://trac.webkit.org/changeset/199155)) - Fixed page tile layers disappearing when graphics acceleration is unavailable ([r199130](https://trac.webkit.org/changeset/199130)) - Made `font-size: 0` render as 0 width when `text-rendering: optimizeLegibility` is used ([r199150](https://trac.webkit.org/changeset/199150)) - Corrected focus ring drawing at incorrect location on image map with a CSS transform ([r199247](https://trac.webkit.org/changeset/199247)) - Made negative `letter-spacing` affect the right edge of the content’s visual overflow ([r199516](https://trac.webkit.org/changeset/199516)) - Corrected compositing for WebGL based canvases after they changed size ([r199536](https://trac.webkit.org/changeset/199536)) - Started clearing the rendered icon on `` when an empty files list is set ([r199540](https://trac.webkit.org/changeset/199540)) - Improved performance of `border-collapse: collapse` on tables ([r199552](https://trac.webkit.org/changeset/199552)) - Improved rendering of `select[multiple]` to better match other browsers ([r199553](https://trac.webkit.org/changeset/199553)) - Fixed backdrop filter so it honors `visibility: hidden` ([r199862](https://trac.webkit.org/changeset/199862)) ### Security - Made nested browsing context created for `