Apple Releases Safari Technology Preview 248 – Brings Bug Fixes and Performance Improvements

Apple has released Safari Technology Preview 248, the latest version of its developer preview web browser. The preview version of Apple’s popular browser offers developers and other interested users the ability to try out features that may or may not, debut in future public release versions of Safari.

‌Safari Technology Preview‌ 248 includes fixes and updates for Accessibility, CSS, Editing, Forms, Images, JavaScript, Media, Navigation, Networking, Rendering, SVG, Scrolling, Security, Storage, Web API, Web Inspector, WebDriver, and WebRTC.

The current ‌Safari Technology Preview‌ release is compatible with machines running macOS 26 Tahoe and macOS 27 Golden Gate, the newest version of macOS that will launch later this year.

The ‌update is available through the Software Update mechanism in System Preferences or System Settings to anyone who has downloaded the browser from Apple’s website.

Overview

Safari Technology Preview Release 248 is now available for download 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: 315567@main…316817@main.

Accessibility

Resolved Issues

• Fixed VoiceOver on Safari unable to navigate to content revealed by disclosure widgets using hidden="until-found". (315964@main) (173228707)
• Fixed stale aria-labelledby when the referenced element dynamically changes its aria-label. (316316@main) (180319221)

CSS

New Features

• Added support for forwarding missing color components when interpolating between analogous color spaces. (315569@main) (180239320)
• Added support for the no-clamp option on the CSS progress() function. (315977@main) (180473472)

Resolved Issues

• Fixed serialization of various CSS at-rules not escaping identifiers. (315795@main) (178750383)
• Fixed :last-child and related selectors incorrectly gating on parser state outside of style resolution. (316495@main) (178879939)
• Fixed changing the color-scheme of an <iframe> not invalidating the appearance of the embedded document. (316467@main) (179177141)
• Fixed CSS scroll snap re-snap to prefer the fragment-targeted (:target) snap area over other aligned snap targets. (315880@main) (180108825)
• Fixed the CSS preload scanner failing to preload @import rules that follow an @layer statement rule. (315576@main) (180170656)
• Fixed serialization of CSSViewTransitionRule. (315614@main) (180170814)
• Fixed MediaList.deleteMedium() to parse its argument as a media query and remove all matching queries. (315579@main) (180270019)
• Fixed MediaList.appendMedium() to parse its argument as a single media query and suppress duplicates. (315594@main) (180291283)
• Fixed grid items with stretch or fit-content preferred sizes computing incorrect minimum-content contributions when sizing tracks. (316296@main) (180748205)
• Fixed inserting a CSS rule while a view transition is active causing the group animation to snap to its final state. (316436@main) (181100818)
• Fixed CSS var() to only resolve its fallback when the first argument resolves to the guaranteed-invalid value. (316280@main) (181114298)
• Fixed navigating away from a render-blocked document before its first rendering opportunity incorrectly firing pagereveal and starting an outbound cross-document view transition. (316446@main) (181191512)

Editing

Resolved Issues

• Fixed drag images of DOM elements with CSS transforms not rendering correctly. (316077@main) (99614217)
• Fixed opaque DOM mutations coming from dictation on iOS. (316049@main) (163454428)
• Fixed deletion in an editable table leaving an empty trailing table row behind. (315990@main) (180877315)
• Fixed vertical caret movement in editable content ignoring the requested editable-type parameter. (316241@main) (181000174)

Forms

Resolved Issues

• Fixed the concentric inner-button corner radius on horizontal text form controls incorrectly ignoring the bottom inset. (316022@main) (180869927)

Images

Resolved Issues

• Fixed a regression where RGB gain map images were decoded to 8 bits per channel, causing a color shift and incorrect brightness. (316069@main) (179152566)
• Fixed handling of the gain-map target pixel format when decoding HDR images to fall back safely when the format cannot be parsed. (316405@main) (181180757)

JavaScript

New Features

• Added support for the TC39 BigInt Math proposal, exposing Math-equivalent methods on BigInt such as BigInt.pow and BigInt.sqrt. (315974@main) (152472996)

Media

Resolved Issues

• Fixed <audio> and <video> controls rendering incorrectly when rotated via CSS transform. (315718@main) (37516619)
• Fixed subtitles and closed captions not appearing in fullscreen video on iPhone. (315789@main) (175298523)
• Fixed ArrayBuffer-backed YUV VideoFrame with a visibleRect rendering with offset chroma channels. (315742@main) (180202939)
• Fixed video playback of streams from certain sources such as security cameras not working. (315774@main) (180411019)
• Fixed transient device rotation resulting in captured video frames having the wrong orientation. (315821@main) (180429147)
• Fixed Media Source Extensions playback and seek by loosening the gap tolerance between buffered ranges. (316146@main) (180439090)

Navigation

Resolved Issues

• Fixed a <meta http-equiv="refresh"> to a URL differing only in fragment identifier being incorrectly treated as a page reload. (316001@main) (176933795)

Networking

Resolved Issues

• Fixed URL path separators being encoded as %2F following a percent-encoded Armenian path segment. (315627@main) (180067095)

Rendering

Resolved Issues

• Fixed the background of a composited <html> element not being repainted when the <body> background changed. (316415@main) (177975964)
• Fixed a regression where block-axis padding on a flex column container with overflow: auto was excluded from scrollHeight. (315813@main) (179376053)
• Fixed an issue where an <img> embedding an SVG with a near-integral intrinsic width rendered one device pixel narrower than expected. (315807@main) (180490343)
• Fixed elements with filter: drop-shadow() not being fully repainted when a child is resized. (316450@main) (181284741)

SVG

Resolved Issues

• Fixed SVG SMIL length animations to reject invalid to, from, and by values such as those with leading whitespace. (315949@main) (118537155)
• Fixed Unicode text with complex scripts not rendering correctly along a curved <textPath>. (316144@main) (120284006)
• Fixed SVGLength.convertToSpecifiedUnits() failing when converting from px to %, em, or ex. (315953@main) (172056830)
• Fixed SVG geometry presentation attributes like cx, cy, r, rx, ry, x, y, width, and height being incorrectly applied to elements such as <g> on which they are not permitted. (315946@main) (175672111)
• Fixed an issue where the per-character rotate attribute was discarded on a <textPath>, so it now composes with the path tangent angle. (315786@main) (178044478)
• Fixed several SVG styling spec-compliance failures. (316174@main) (181052042)
• Fixed dynamic changes to orient and markerUnits on <marker> not repainting elements that reference it. (316350@main) (181106538)
• Fixed SVG SMIL number, integer-optional-integer, number-optional-number, and path animations to not apply when their from, to, or by values fail to parse. (316468@main) (181308150)

Scrolling

Resolved Issues

• Fixed CSS scroll snap points inside zero-sized elements not working correctly. (315948@main) (172863699)
• Fixed CSS scroll snap re-snap to prefer a snap area that contains the focused or fragment-targeted element. (315927@main) (180707984)

Security

Resolved Issues

• Fixed a regression where some websites failed to display and logged Content Security Policy errors in the console. (316290@main) (179684592)
• Fixed same-page navigations being incorrectly checked against Content Security Policy. (315759@main) (180342503)
• Fixed Content Security Policy frame-ancestors violations in report-only policies being ignored instead of reported. (315753@main) (180447621)
• Fixed Content Security Policy parsing to reject trailing characters after the closing quote on nonce-source and hash-source values. (316008@main) (180903857)
• Fixed Content Security Policy trusted-types expressions to reject trailing characters after keywords and the wildcard. (316089@main) (180973793)

Storage

Resolved Issues

• Fixed an issue where IndexedDB transactions could be blocked for an extended period before starting when another page’s transaction was suspended in the background. (315609@main) (178769599)

Web API

Resolved Issues

• Fixed the Async Clipboard API to request paste access asynchronously. (315997@main) (75969974)
• Fixed Digital Credentials to surface OperationError for platform-cancellation and unknown errors instead of AbortError or UnknownError. (315973@main) (174308268)
• Fixed Digital Credentials rejecting with the wrong error code and synchronously; rejections are now queued as a task with the correct error. (315895@main) (174895437)
• Fixed KeyboardEvent.getModifierState("AltGraph") and MouseEvent.getModifierState("AltGraph") always returning false. (315804@main) (180597374)
• Fixed Credential.type returning "digital-credential" instead of "digital" for digital credentials. (315891@main) (180618646)
• Fixed aborting navigator.credentials.get() leaving the digital-credentials document picker stuck on screen. (316494@main) (180812397)
• Fixed FileReader.readAsText() ignoring the charset parameter of the Blob’s MIME type. (315996@main) (180890703)

Web Inspector

Resolved Issues

• Fixed showing ES2022 class private fields, methods, and accessors when inspecting object instances in the Console. (316171@main) (88527162)
• Fixed symbolic breakpoints in the debugger so they work with intrinsic functions. (315713@main) (99037335)
• Fixed a JavaScript breakpoint on a line containing only a semicolon not being triggered. (316519@main) (126707973)
• Fixed the Console REPL to allow redefinition of variables declared with let and const. (316523@main) (143140659)
• Fixed the Timeline exporting and importing the wrong timestamp for performance.mark() records. (316073@main) (145226764)
• Fixed local response overrides mapped to a file being interpreted as Latin-1 (ISO-8859-1) instead of their actual encoding. (316074@main) (149847746)
• Fixed the Media Logging setting not persisting across page loads. (315758@main) (154766890)
• Fixed symbolic breakpoints to work with native constructors such as Array, Date, EventTarget, and Worker. (316262@main) (157178256)
• Fixed missing stack traces for MIME type errors when importing modules. (316529@main) (169396940)
• Fixed the Accessibility sidebar being empty for nodes inside cross-origin iframes. (316399@main) (178562336)
• Fixed inline style invalidation to batch DOM.getAttributes commands per tick in cross-origin iframes instead of issuing one command per node. (316487@main) (178830496)
• Fixed DOM Storage read and write commands to resolve against the frame’s own origin in cross-origin iframes. (316501@main) (179249711)
• Fixed a moved breakpoint reverting to its original location after closing and reopening Web Inspector. (315585@main) (180083858)
• Fixed showing the formatted parameters string for prototype objects such as Map.prototype. (315599@main) (180298712)
• Fixed missing formatted parameter strings for object shorthand methods and arrow functions. (315723@main) (180466459)
• Fixed an unnecessary colon appearing in front of non-class function properties. (315731@main) (180476445)
• Fixed a self-canceling ternary that produced an incorrect cross-axis direction in the flex overlay. (316429@main) (181198803)
• Fixed the color picker force-converting picked colors to Display P3. (316419@main) (181201503)
• Fixed Page.searchInResources silently omitting cache-backed resources from search results. (316421@main) (181202027)
• Fixed duplicate invalid CSS declarations both incorrectly displaying as Active in the Styles sidebar. (316418@main) (181203080)
• Fixed adopted constructable stylesheets being misclassified as User Agent stylesheets in cross-origin iframes. (316433@main) (181204768)
• Fixed an unsigned underflow that caused the DOM agent to spuriously report power-efficient playback. (316443@main) (181205602)
• Fixed Network.setExtraHTTPHeaders to replace previously set headers instead of accumulating them. (316444@main) (181282814)

WebDriver

New Features

• Added WebDriver support for the Digital Credentials API, including commands to simulate wallet payloads, indefinite waits, and user rejection. (316435@main) (168941907)

WebRTC

Resolved Issues

• Fixed the WebProcess AudioSession to remain active while microphone capture is live. (316394@main) (180505014)
• Fixed the configurationchange event being dropped when a source-side change occurred while a MediaStreamTrack was muted; the event is now deferred until unmute. (316301@main) (180728609)

Apple’s aim with ‌Safari Technology Preview‌ is to gather feedback from developers and users on its browser development process. ‌Safari Technology Preview‌ can run side-by-side with the existing Safari browser and while it is designed for developers, it does not require a developer account to download and use.