What's new in March's browser releases

Chrome 146, Firefox 149, and Safari 26.4 all shipped to stable in March, bringing a mix of layout, animation, and API features. Here's a look at the notable additions across the three browsers.

Masonry layout arrives in Safari

Safari 26.4 is the first stable release to support display: grid-lanes, the property value that enables masonry-style layout in CSS Grid. This gives developers a native way to create Pinterest-style columns without resorting to JavaScript-based solutions.

Container queries without conditions

Firefox 149 and Safari 26.4 both add support for @container rules that specify only a container name and no size or style conditions. This allows you to target elements purely by their container context, which simplifies styling when you don't need to check dimensions or other property values.

Scroll-driven animation controls

Chrome 146 enables animations that respond to scroll position using declarative CSS. Animations are offloaded to a worker thread for better performance, and there are accompanying JavaScript interfaces for the Web Animations API. The same release also introduces trigger-scope, which restricts the visibility of animation trigger names so they don't collide globally across the document.

Refined popover behavior in Firefox

Firefox 149 now understands the hint value of the popover global attribute. A hint popover will not dismiss an open auto popover, but it will close other hint popovers. This distinction gives developers finer control over how multiple popovers interact on the page.

Responsive image sizing improvements

Safari 26.4 lets you use the min(), max(), and clamp() CSS math functions inside the sizes attribute of an <img> element. That makes it easier to express responsive image width conditions that depend on fluid layouts.

JavaScript iterator sequencing

Chrome 146 and Safari 26.4 implement Iterator.concat(...items), a static method that returns an iterator chaining together one or more existing iterators. The feature is now considered Baseline Newly available across the major engines.

Native close handling for custom components

Firefox 149 adds the CloseWatcher interface, which lets custom UI components react to platform-native close gestures such as the Esc key or the Back button on Android. This aligns third-party dialogs and menus with how built-in browser UI elements behave.

Previews from beta channels

March also saw the release of Chrome 147 beta and Firefox 150 beta, which preview features due in Aprils's stable releases.

Chrome 147 beta includes the contrast-color() CSS function that returns either black or white based on which offers better contrast against its argument. It also adds border-shape and element-scoped view transitions. Firefox 150 beta previews the revert-rule CSS keyword, customeElementRegistry support on Elements and DocumentOrShadowRoot, and light-dark() applied to images.