March has always been a busy month for WebKit, and Safari 26.4 continues that tradition with a massive update. This release packs 44 new features, 191 bug fixes, and one deprecation, all aimed at making web development smoother and more powerful. The team listened to 2025 developer surveys, focusing on stability, consistency, and closing gaps in web standards. Here are the seven most important updates you need to know.
1. CSS Grid Lanes: The Masonry Layout You've Been Waiting For
After years of anticipation, CSS Grid Lanes finally brings masonry-style layouts to Safari. This feature lets you create rich visual galleries, magazine-like grids, and dynamic content arrangements without JavaScript hacks or complex workarounds. Think of Pinterest-style columns that automatically fill in gaps—but now natively in CSS. Developers can use grid-template-rows: masonry to flow items into optimal positions based on available space. This is a game-changer for designers who need flexible, responsive layouts that adapt to varying content heights. Safari 26.4 is among the first browsers to ship this, putting WebKit ahead in the web platform evolution.
2. WebTransport: Low-Latency Communication Redefined
WebTransport offers a modern alternative to WebSocket, built on top of HTTP/3 and QUIC. It reduces latency dramatically, making it perfect for real-time applications like multiplayer games, live collaborative editing tools, and video conferencing. Unlike WebSocket, WebTransport supports multiple streams and unreliable data modes (like UDP), giving developers fine-grained control over data delivery. This means smoother gaming, faster chat updates, and more responsive web apps. Safari 26.4 adds full support, so you can start experimenting with this powerful API today. For a deep dive, check out the developer stability section below.
3. Keyboard Lock API: Full Control for Web Apps
Web apps often struggle with keyboard shortcuts when running in full-screen mode. The Keyboard Lock API solves this by letting developers capture and handle all keyboard input, even keys normally reserved by the browser like F11 or Ctrl+W. This is crucial for applications like code editors, graphic design tools, and virtual desktops where custom key bindings are essential. Safari 26.4 implements this API, bringing desktop-class keyboard control to web apps on iOS and macOS. Combined with the CSS Grid Lanes layout, it makes Safari a serious platform for complex web-based software.
4. CSS Functions in the sizes Attribute: A Long-Awaited Fix
WebKit has supported CSS min() and max() since 2018, and the sizes attribute for responsive images since 2014—but you couldn't use them together until now. In Safari 26.4, you can write something like sizes="(min-width: 800px) min(50vw, 400px), 100vw" to create truly adaptive image sizes. This closes a standards gap that affected other browsers, ensuring that WebKit now matches the latest CSS specification. It's a small change with big impact for responsive design, making it easier to serve appropriately sized images without JavaScript. Developers have been asking for this consistency, and Safari delivered.
5. 191 Bug Fixes: Focus on SVG, Tables, MathML, and CSS Zoom
Safari 26.4 includes 191 fixes, targeting areas that matter most to developers. SVG handling improvements make vector graphics render more predictably. Table layout fixes resolve long-standing issues with column widths and border rendering. MathML updates enhance accessibility for scientific content. And CSS Zoom now works more consistently across elements, reducing surprises in responsive designs. WebKit engineers dug deep into these areas, driven by developer feedback. If you've been struggling with any of these, test your site in Safari 26.4—chances are the issue is resolved. For more details on what was fixed, see the layout engine rewrite.
6. Layout Engine Rewrite: Blocks-in-Inline Complete, Flexbox Next
WebKit continues its multi-year layout engine overhaul. In Safari 26.4, the blocks-in-inline layout is fully implemented, fixing many edge cases with nested block elements inside inline contexts. Work on Flexbox is ongoing, and the team has now begun rewriting CSS Grid for even better performance and spec compliance. This is a massive under-the-hood effort that will eventually make all layout modes faster and more reliable. While many changes are invisible to developers, they reduce bugs and improve rendering consistency across all Apple platforms—from watchOS to visionOS.
7. Developer-First Stability: Listening and Responding
The biggest theme of Safari 26.4 is stability. The WebKit team analyzed 2025 developer surveys and prioritized bug fixes over new features. Many updates bring existing features in line with the latest web standards rather than adding novelty. If you encounter a bug, the team encourages you to file it at bugs.webkit.org with concrete examples—like links to affected sites, code snippets, or user stories. Multiple reports help prioritize what matters most. Safari 26.4 proves that when developers speak, WebKit listens. This release is a direct response to the community's call for fewer surprises and more reliability.
Safari 26.4 marks a shift toward refinement and responsiveness. With features like CSS Grid Lanes, WebTransport, and the Keyboard Lock API, alongside hundreds of fixes, it's a release built for real-world web development. The layout engine rewrite promises even better performance ahead. Test your projects and let the team know what still needs work—your feedback shapes future updates. This isn't just a software release; it's a partnership between WebKit engineers and the developer community.