What Changed in WebKit: Safari 18.3
WebKit EngineWhy This Matters
WebKit powers every browser on iOS and iPadOS, plus Safari on macOS and visionOS. Safari 18.3 is a quality-focused release — just 1 new feature, but 23 targeted bug fixes that polish the major features introduced in Safari 18.0–18.2. It ships with iOS 18.3, macOS Sequoia 15.3, and visionOS 2.3.
CSS
The big features from 18.2 get important fixes. View Transitions see the ::view-transition pseudo-element corrected to properly create a stacking context — a subtle but critical rendering fix for sites using layered transition animations. text-box is fixed for buttons, where the new trim behavior wasn’t applying correctly.
:not(:has(...)) invalidation is corrected, fixing a selector combination that could fail to update when DOM changes occurred. content-visibility: auto now properly displays SVG text in hidden subtrees, and background-origin defaults correctly to border-box for the new border-area clip value.
JavaScript
No new JavaScript features in this release, but the stability focus is evident in the editing and DOM fixes that affect JavaScript-heavy applications.
Web APIs
Popover behavior is fixed on iOS and iPadOS — touching or clicking outside a popover now correctly closes it, resolving a fundamental interaction bug. Pointer Events for coalesced and predicted events now carry the same pointer identifier as their parent event, fixing inconsistencies that could break drawing and gesture-tracking applications.
Web Extensions get 2 fixes: a permissions alert no longer incorrectly appears when clicking an extension icon after granting access, and browser.tabs.create now properly respects pinned and openerTabId attributes on iOS.
Media
An aspect ratio fix for WebM files corrects rendering when source pixels have a non-1:1 sample-aspect-ratio — a bug that could cause video to appear stretched or squished on sites using VP9/WebM content.
Security
The Clear-Site-Data: "executionContexts" directive is removed, aligning with the specification change that deprecated this value. This is the release’s single deprecation.
SVG paths clipping at tile boundaries is fixed, preventing visual artifacts that could expose content incorrectly in certain rendering scenarios.
Performance
View Transitions performance improves with a change to only rasterize on-screen snapshots — previously, off-screen transition elements could consume GPU resources unnecessarily. WebAssembly memory leaks in Table objects are fixed, improving stability for applications that extensively create and manage WASM instances.
Scrollbar rendering is polished: dynamically changing scrollbar-width no longer causes horizontal scrollbars to paint incorrectly, and scrollbar appearance now properly updates when switching between light and dark mode.
An element with height: min-content no longer gets incorrectly stretched vertically — a layout fix that could affect card-based designs and flex/grid layouts.
Editing & Input
Several editing fixes improve daily browsing: duplicated highlights in iCloud Notes are corrected, getRangeAt(0) now returns updated objects after selection changes (fixing a bug that could break rich text editors), and users can again tap to place the cursor at the end of a line after autocorrect.
The drag preview no longer remains on screen after cancelling a multi-item drag operation.
Bottom Line
Who should care? If you adopted View Transitions, text-box, or popover from Safari 18.0–18.2, this update fixes real bugs you may have encountered. Extension developers on iOS should update to get tab creation working properly. And anyone using WebAssembly at scale benefits from the memory leak fix.
Biggest impact: The View Transitions stacking context fix and the popover dismiss fix are the most practically significant — they address behaviors that could make or break real-world implementations of these new web platform features. Safari 18.3 is the “you can now safely use the 18.2 features in production” release.