# Safari Technology Preview 256 Release Notes Learn about the latest web technology updates in Safari Technology Preview: Accessibility, Animations, CSS, Canvas, Forms, HTML, Images, JavaScript, Media, Networking, Performance, Rendering, SVG, Security, Web API, Web Extensions, Web Inspector, WebAssembly, WebGL, WebGPU, and WebRTC. ## Overview [Safari Technology Preview](https://webkit.org/blog/6017/introducing-safari-technology-preview/) Release 256 is now [available for download](https://developer.apple.com/safari/resources/) for macOS Golden Gate and macOS Tahoe. If you already have Safari Technology Preview installed, you can update it in System Settings under General → Software Update. This release includes WebKit changes between: [323398@main…324653@main](https://github.com/WebKit/WebKit/compare/8fd906a4024b97a7d373f172e6c8492696ea2c99...ed7c100c4c4d89db54934fa07b3019a2270c7ac3). ### Accessibility #### Resolved Issues - Fixed list marker text generated with the `content` property not being exposed in the accessibility tree. ([323578@main](https://commits.webkit.org/323578@main)) (189838099) - Fixed VoiceOver being unable to reach the content of an iframe nested inside an iframe with `role="none"` or `role="presentation"`. ([323749@main](https://commits.webkit.org/323749@main)) (189901948) ### Animations #### Resolved Issues - Fixed scroll-driven animations drawing a `translate` keyframe of `none` as the element’s own `translate` value. ([323583@main](https://commits.webkit.org/323583@main)) (189882533) - Fixed: Improved performance of scroll-driven animations by avoiding style invalidation on animation updates when timing is unchanged. ([324449@main](https://commits.webkit.org/324449@main)) (190709310) ### CSS #### New Features - Added support for `text-combine-upright` on `::marker`. ([323582@main](https://commits.webkit.org/323582@main)) (189912173) - Added support for `continue: collapse` with `line-clamp`, which is now set by the `line-clamp` shorthand. ([323734@main](https://commits.webkit.org/323734@main)) (190023170) - Added support for `font-palette-mix()` on Cocoa platforms, allowing font color palettes to be blended. ([324044@main](https://commits.webkit.org/324044@main)) (190133191) #### Resolved Issues - Fixed `::highlight()` styles not being found past anonymous boxes. ([323588@main](https://commits.webkit.org/323588@main)) (148245032) - Fixed text zoom being applied twice to font sizes specified with font-relative units. ([324195@main](https://commits.webkit.org/324195@main)) (188215447) - Fixed `aspect-ratio` interpolation being inverted in vertical writing modes. ([323584@main](https://commits.webkit.org/323584@main)) (188500448) - Fixed `document.fonts.ready` never resolving when an unused `@font-face` has a failing `local()` source followed by a `url()` source. ([323883@main](https://commits.webkit.org/323883@main)) (189243828) - Fixed layout not updating inside a nested scroll container after its classic scrollbar disappears when using `line-clamp` with an absolutely positioned descendant. ([324368@main](https://commits.webkit.org/324368@main)) (189451731) - Fixed `:dir()` matching for a `` element without a `dir` attribute so it updates when its ancestor’s direction changes. ([323439@main](https://commits.webkit.org/323439@main)) (189472957) - Fixed `light-dark()` inside `image-set()` incorrectly accepting a bare string as an image URL. ([323705@main](https://commits.webkit.org/323705@main)) (189627071) - Fixed `CSSStyleSheet.replaceSync()` on a detached constructed stylesheet appending rules instead of replacing them, which could also corrupt other stylesheets sharing the same contents. ([323736@main](https://commits.webkit.org/323736@main)) (189634428) - Fixed `CSSMatrixComponent.toMatrix()` returning the component’s internal `DOMMatrix` for 3D matrices, so mutating the result no longer changes the component. ([323948@main](https://commits.webkit.org/323948@main)) (189653766) - Fixed a positioned `inline-block` after the `line-clamp` clamp point remaining visible. ([323402@main](https://commits.webkit.org/323402@main)) (189672687) - Fixed `-webkit-min-device-pixel-ratio` and `-webkit-max-device-pixel-ratio` media features serializing as `min--webkit-device-pixel-ratio` and `max--webkit-device-pixel-ratio`. ([323731@main](https://commits.webkit.org/323731@main)) (189687289) - Fixed a flex item with `aspect-ratio` and a `calc()` height resolving to a zero flex base size. ([323464@main](https://commits.webkit.org/323464@main)) (189753886) - Fixed `CSSStyleDeclaration.setProperty()` to override an existing `!important` custom property when called without a priority. ([324083@main](https://commits.webkit.org/324083@main)) (189765758) - Fixed a table flex item with borders being wider than its content and borders. ([323471@main](https://commits.webkit.org/323471@main)) (189766215) - Fixed `line-clamp: auto` to account for collapsed block-end margins when finding the clamp point. ([323468@main](https://commits.webkit.org/323468@main)) (189767053) - Fixed a table flex item with borders or padding and a non-auto `min-width` being too wide. ([323466@main](https://commits.webkit.org/323466@main)) (189768684) - Fixed the `grid-template` shorthand so empty `[]` line names before a row’s leading line names no longer overwrite the previous row’s track size. ([323665@main](https://commits.webkit.org/323665@main)) (189769011) - Fixed `line-clamp: auto` to find the clamp point before balancing content. ([323481@main](https://commits.webkit.org/323481@main)) (189774214) - Fixed `calc()` negation of a typed-arithmetic product flipping the sign of every factor. ([323577@main](https://commits.webkit.org/323577@main)) (189779826) - Fixed `object-fit: none` and `object-fit: scale-down` to size an image without natural dimensions against its content box. ([323503@main](https://commits.webkit.org/323503@main)) (189844957) - Fixed the content size suggestion of grid items with a preferred aspect ratio to be clamped correctly in grid layout. ([323655@main](https://commits.webkit.org/323655@main)) (189848571) - Fixed: Changed the `auto` value of the `continue` property to `normal` to match the specification. ([323557@main](https://commits.webkit.org/323557@main)) (189893145) - Fixed the grid layout engine to compute collapsed tracks for `repeat(auto-fit)`. ([323658@main](https://commits.webkit.org/323658@main)) (189937668) - Fixed a regression where `word-break: keep-all` allowed many incorrect line breaks. ([324360@main](https://commits.webkit.org/324360@main)) (189973862) - Fixed the placement of outside list markers in vertical writing modes. ([323721@main](https://commits.webkit.org/323721@main)) (190017212) - Fixed grid layout to collapse empty `repeat(auto-fit)` tracks and their gutters. ([323843@main](https://commits.webkit.org/323843@main)) (190062840) - Fixed grid layout to use the transferred size suggestion for the automatic minimum size of grid items. ([323855@main](https://commits.webkit.org/323855@main)) (190065310) - Fixed the intrinsic minimum block size of a column flex item being incorrectly clamped by a smaller `max-block-size`. ([323872@main](https://commits.webkit.org/323872@main)) (190077511) - Fixed selectors with mixed-case attribute names failing to match HTML elements in XHTML documents when used with ancestor combinators. ([323947@main](https://commits.webkit.org/323947@main)) (190089102) - Fixed `CSSUnitValue` for container query length units reporting a number type instead of a length type. ([323949@main](https://commits.webkit.org/323949@main)) (190095825) - Fixed the `linear()` easing function rejecting a percentage written before the number in a control point. ([323951@main](https://commits.webkit.org/323951@main)) (190097099) - Fixed `calc()` type inversion overflowing its exponent, which could produce incorrect results. ([323873@main](https://commits.webkit.org/323873@main)) (190099592) - Fixed `CustomStateSet` `add()` and `delete()` invalidating style when the set does not change. ([323982@main](https://commits.webkit.org/323982@main)) (190183292) - Fixed the `CSSCounterStyleRule.name` setter not updating the `name` getter or `cssText`. ([324049@main](https://commits.webkit.org/324049@main)) (190185460) - Fixed a grid item with a non-auto `min-block-size` overflowing the grid when the grid shrinks and the item’s content wraps. ([324127@main](https://commits.webkit.org/324127@main)) (190192125) - Fixed quote marks generated by `open-quote` and `close-quote` not taking the `::first-line` style. ([324380@main](https://commits.webkit.org/324380@main)) (190252758) - Fixed a stretched item in a `column-reverse` wrapping flex container ignoring its main-axis `auto` margin. ([324398@main](https://commits.webkit.org/324398@main)) (190272880) - Fixed `calc-size(auto, size)` making an `aspect-ratio` box wider than its max-content size when a child has a percentage height. ([324649@main](https://commits.webkit.org/324649@main)) (190727077) - Fixed an absolutely positioned box inside content after the `line-clamp` clamp point not being laid out. ([324457@main](https://commits.webkit.org/324457@main)) (190732934) - Fixed an orthogonal block-level box inside an inline box incorrectly adding its top and bottom margins to its container’s width. ([324652@main](https://commits.webkit.org/324652@main)) (190767962) ### Canvas #### New Features - Added the `lang` attribute to `CanvasTextDrawingStyles`. ([324596@main](https://commits.webkit.org/324596@main)) (143391479) - Added support for `fontKerning`, `fontStretch`, `fontVariantCaps`, and `textRendering` in canvas text drawing styles. ([324110@main](https://commits.webkit.org/324110@main)) (190388702) - Added support for the `inherit` value of the `direction` attribute in `CanvasTextDrawingStyles`. ([324603@main](https://commits.webkit.org/324603@main)) (190908024) #### Resolved Issues - Fixed black pixel artifacts when drawing a Canvas 2D image through WebGL after applying a gradient. ([324218@main](https://commits.webkit.org/324218@main)) (189661903) - Fixed drawing a `VideoFrame` in BGRX format to ignore the alpha component. ([323809@main](https://commits.webkit.org/323809@main)) (189794952) ### Forms #### Resolved Issues - Fixed `appearance: base-select` option hover styling being clipped when rotated transforms are applied. ([323903@main](https://commits.webkit.org/323903@main)) (171933742) - Fixed the date picker not using the correct appearance when automatic dark mode is applied. ([324046@main](https://commits.webkit.org/324046@main)) (188747558) - Fixed `` elements so they update at the correct times in an enhanced `` so it always selects the first option. ([323929@main](https://commits.webkit.org/323929@main)) (190021473) - Fixed: Updated the default `` element triggered a Content Security Policy `style-src-attr` violation. ([324283@main](https://commits.webkit.org/324283@main)) (189869066) - Fixed frames in an `about:blank` popup not being treated as secure contexts. ([323985@main](https://commits.webkit.org/323985@main)) (190126073) - Fixed `data:` documents so that only top-level `data:` documents are treated as non-secure contexts. ([324086@main](https://commits.webkit.org/324086@main)) (190309192) - Fixed Geolocation to be blocked in non-secure contexts. ([324227@main](https://commits.webkit.org/324227@main)) (190455029) ### Web API #### New Features - Added support for the `estimated` line item type in Apple Pay JS. ([324470@main](https://commits.webkit.org/324470@main)) (187363098) - Added support for `VideoFrame.copyTo()` converting to RGB on the fly. ([323866@main](https://commits.webkit.org/323866@main)) (189797745) - Added support for the `colorSpace` option in `VideoFrame.copyTo()`. ([323952@main](https://commits.webkit.org/323952@main)) (189902908) #### Resolved Issues - Fixed `document.fullscreenEnabled` and `document.webkitFullscreenEnabled` to return consistent values. ([323549@main](https://commits.webkit.org/323549@main)) (102937855) - Fixed `element.checkVisibility()` to work for unslotted elements. ([324155@main](https://commits.webkit.org/324155@main)) (118648432) - Fixed the AAC `AudioEncoder` producing an incorrect decoder config description. ([324436@main](https://commits.webkit.org/324436@main)) (164878480) - Fixed `getComposedRanges()` over-rescoping the range when a passed shadow root is a descendant of the boundary’s shadow tree. ([324385@main](https://commits.webkit.org/324385@main)) (180810983) - Fixed the Navigation API so `navigation.back()` and `navigation.traverseTo()` on the main frame land on the correct session history entry after a subframe has navigated. ([324589@main](https://commits.webkit.org/324589@main)) (187959384) - Fixed `element.checkVisibility()` returning `false` for `` elements in a list box. ([323990@main](https://commits.webkit.org/323990@main)) (189211521) - Fixed `getBoundingClientRect()` returning incorrect boxes for `` elements in a list box. ([324424@main](https://commits.webkit.org/324424@main)) (189227828) - Fixed `VideoFrame`, `AudioData`, `EncodedVideoChunk`, `EncodedAudioChunk`, `MediaStreamTrack`, and `MediaStreamTrackHandle` so they can no longer be cloned or transferred into a different agent cluster. ([323558@main](https://commits.webkit.org/323558@main)) (189747796) - Fixed `VideoFrame.copyTo()` to succeed for BGRX and RGBX frames. ([323569@main](https://commits.webkit.org/323569@main)) (189797144) - Fixed Media Session artwork images that have no intrinsic size, such as SVG without `width`, `height`, or `viewBox`, so they are sized using the default sizing algorithm with a 512x512 ideal artwork size. ([323461@main](https://commits.webkit.org/323461@main)) (189822449) - Fixed `VideoFrame.copyTo()` to allow converting to an RGB format when `VideoFrame.format` is `null`. ([323953@main](https://commits.webkit.org/323953@main)) (189932876) - Fixed an issue where a page navigated to `about:blank` lost its history entry when the next navigation occurred. ([324566@main](https://commits.webkit.org/324566@main)) (190237322) - Fixed an issue where a previous tap could cause a later tap to be treated as a hover. ([324259@main](https://commits.webkit.org/324259@main)) (190357260) - Fixed `Blob`’s `text()` to no longer sniff UTF-16 byte order marks when decoding. ([324134@main](https://commits.webkit.org/324134@main)) (190382159) - Fixed a navigation to the current URL reporting the wrong `navigationType` when `document.domain` is set. ([324269@main](https://commits.webkit.org/324269@main)) (190420617) - Fixed `Blob`’s `text()` to decode its data as it arrives. ([324356@main](https://commits.webkit.org/324356@main)) (190449988) - Fixed `location.replace()` on a frame in another process so it no longer adds a session history entry. ([324264@main](https://commits.webkit.org/324264@main)) (190512610) - Fixed an issue where `setInterval()` could be scheduled using a stale cached next fire time. ([324432@main](https://commits.webkit.org/324432@main)) (190658646) - Fixed an issue where navigating an iframe away from its initial `about:blank` document by clicking a link added a history entry. ([324562@main](https://commits.webkit.org/324562@main)) (190687356) - Fixed `requestIdleCallback()` idle period scheduling by using the actual frame period at 60Hz, so idle periods are no longer scheduled right before the frame deadline. ([324545@main](https://commits.webkit.org/324545@main)) (190768899) #### Deprecations - Deprecated XML external entities, and added a console warning when they are used. ([324200@main](https://commits.webkit.org/324200@main)) (184870654) ### Web Extensions #### Resolved Issues - Fixed `tabs.onUpdated` to not report unchanged values and to report rapid property toggles. ([324357@main](https://commits.webkit.org/324357@main)) (84204907) - Fixed Safari showing no error when the `declarativeNetRequest` `rule_resources` JSON is not a list. ([323963@main](https://commits.webkit.org/323963@main)) (146113788) - Fixed calling `action.setPopup()` with an invalid popup path leaving the popup unrecoverably broken. ([324142@main](https://commits.webkit.org/324142@main)) (166048992) - Fixed non-repeating `browser.alarms` alarms not being removed from the alarm map after firing. ([323750@main](https://commits.webkit.org/323750@main)) (173399426) - Fixed `action.setIcon()` throwing an error when `tabId` is `null` instead of setting the global icon. ([324277@main](https://commits.webkit.org/324277@main)) (176975795) - Fixed `runtime.openOptionsPage()` so it focuses the existing options page when it is already open. ([324541@main](https://commits.webkit.org/324541@main)) (177344808) - Fixed `browser.alarms.clearAll()` to return a `Promise`. ([323534@main](https://commits.webkit.org/323534@main)) (187115327) - Fixed `alarms.onAlarm` to report the next `scheduledTime` for repeating alarms when the background page was unloaded. ([323752@main](https://commits.webkit.org/323752@main)) (189951123) - Fixed an issue where an extension’s own content rule lists were applied to pages other than its extension pages. ([323863@main](https://commits.webkit.org/323863@main)) (190036270) - Fixed content blocker rules that combine `request-method` with a top URL or frame URL condition not working. ([324050@main](https://commits.webkit.org/324050@main)) (190316684) ### Web Inspector #### New Features - Added display of `::slotted()` styles in the Styles sidebar of the Elements tab. ([323654@main](https://commits.webkit.org/323654@main)) (29035069) - Added support for exposing Shadow DOM parts in the Elements tab. ([323685@main](https://commits.webkit.org/323685@main)) (100250231) - Added reporting of rendered font character ranges. ([324359@main](https://commits.webkit.org/324359@main)) (143740107) - Added visual distinction for private methods in the Console. ([324399@main](https://commits.webkit.org/324399@main)) (190664079) #### Resolved Issues - Fixed `::placeholder` styles for `input` elements not showing up in the Styles sidebar. ([323670@main](https://commits.webkit.org/323670@main)) (56514581) - Fixed a regression where `console.group` and `console.groupCollapsed` did not always encapsulate grouped messages. ([323613@main](https://commits.webkit.org/323613@main)) (142028751) - Fixed `toString` being called twice when logging an object with the console. ([323668@main](https://commits.webkit.org/323668@main)) (169883641) - Fixed a discrepancy where Web Inspector and WebDriver reported different computed roles for the same element. ([323965@main](https://commits.webkit.org/323965@main)) (179841782) - Fixed: Improved Web Inspector performance by no longer iterating all rendering frame records to calculate the overview graph height. ([323614@main](https://commits.webkit.org/323614@main)) (181921116) - Fixed the Elements tab to collect CSS variables for both styles and keyframes. ([323598@main](https://commits.webkit.org/323598@main)) (189934225) - Fixed the Elements tab to correctly parse animation names when editing keyframes. ([323600@main](https://commits.webkit.org/323600@main)) (189934494) - Fixed `console` screenshots appearing in read-only Timelines recordings. ([323599@main](https://commits.webkit.org/323599@main)) (189934498) - Fixed markers appearing in read-only Timelines recordings. ([323601@main](https://commits.webkit.org/323601@main)) (189934611) - Fixed the Timelines tab to stop updating the time when capture is inactive. ([323604@main](https://commits.webkit.org/323604@main)) (189936051) - Fixed Web Inspector to handle URLs with an empty host. ([323603@main](https://commits.webkit.org/323603@main)) (189936372) - Fixed Web Inspector to parse URLs with ports and `blob:` URLs in stack traces. ([323606@main](https://commits.webkit.org/323606@main)) (189936384) - Fixed the Timelines tab to show capture progress only for the active recording. ([323607@main](https://commits.webkit.org/323607@main)) (189936469) - Fixed the Elements tab to correctly parse animation keys when editing keyframes. ([323608@main](https://commits.webkit.org/323608@main)) (189936580) - Fixed the Console’s `await` convenience being included in code completion requests. ([323605@main](https://commits.webkit.org/323605@main)) (189936602) - Fixed the Timelines tab to preserve imported heap snapshots when exporting recordings. ([323609@main](https://commits.webkit.org/323609@main)) (189936631) - Fixed stack trace popovers to reposition when the Web Inspector window is resized. ([323611@main](https://commits.webkit.org/323611@main)) (189936790) - Fixed Web Inspector to distinguish the source code of multiple `Worker` instances. ([323612@main](https://commits.webkit.org/323612@main)) (189936821) - Fixed awaited evaluation in the Console to preserve the selected call frame scope. ([323610@main](https://commits.webkit.org/323610@main)) (189937067) - Fixed the Elements tab to refresh styles after a CSS grouping rule edit fails. ([323616@main](https://commits.webkit.org/323616@main)) (189937131) - Fixed the Elements tab to also track inherited CSS variable dependencies. ([323623@main](https://commits.webkit.org/323623@main)) (189939830) - Fixed Web Inspector to report errors that occur while loading source maps. ([323653@main](https://commits.webkit.org/323653@main)) (189956520) - Fixed the Elements tab overlay for SVG `` nodes appearing in the wrong position. ([324055@main](https://commits.webkit.org/324055@main)) (190158402) - Fixed Web Inspector so that edits to a style sheet mutate the live style sheet contents. ([323979@main](https://commits.webkit.org/323979@main)) (190235686) - Fixed links to inline CSS in Web Inspector incorrectly adding the starting column of the `