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New to the web platform in March

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Discover some of the interesting features that have landed in stable and beta web browsers during March 2025.

Published: March 31, 2025

Stable browser releases

In March 2025 Firefox 136, Chrome 134, and Safari 18.4 became stable. This post looks at the new features added to the web platform.

New pseudo-classes :has-slotted and :open

Firefox 136 supports the :has-slotted pseudo-class, used to style elements in <template> that have content added to a <slot> element when rendering a web component.

Browser Support

  • Chrome: 134.
  • Edge: 134.
  • Firefox: 136.
  • Safari: not supported.

Source

The :open pseudo-class lets you select any element that is currently in an open state. This applies to the <details>, <dialog>, <input> elements with a picker, and <select> elements when a drop-down selection box is open.

Browser Support

  • Chrome: 133.
  • Edge: 133.
  • Firefox: 136.
  • Safari: not supported.

Source

Intl.DurationFormat

Firefox 136 also supports Intl.DurationFormat. This lets you format durations, taking locale into account. This feature joins Baseline, and you can find out more in Intl.DurationFormat is now Baseline Newly available.

Browser Support

  • Chrome: 129.
  • Edge: 129.
  • Firefox: 136.
  • Safari: 16.4.

Source

The plaintext-only value of the contenteditable attribute

Another feature becoming Baseline Newly available in this release of Firefox is the plaintext-only value of the contenteditable global attribute. Read about this value in The contenteditable "plaintext-only" attribute value combination is now Baseline Newly available.

Browser Support

  • Chrome: 51.
  • Edge: 12.
  • Firefox: 136.
  • Safari: ≤13.1.

Sideways writing modes for CSS

Safari 18.4 includes support for writing-mode: sideways-rl and writing-mode: sideways-lr. These values are used when you want to display text vertically for presentational reasons. They should now become Baseline Newly available.

Browser Support

  • Chrome: 132.
  • Edge: 132.
  • Firefox: 43.
  • Safari: 18.4.

The CSS shape() function

Also in Safari 18.4 is the CSS shape() function, allowing for responsive free-form shapes in clip-path.

Browser Support

  • Chrome: 135.
  • Edge: 135.
  • Firefox Technology Preview: supported.
  • Safari: 18.4.

Source

ClipboardItem.support()

Safari 18.4 implements the support() method for ClipboardItem(). This lets you see which formats are supported during clipboard operations, and is now Baseline Newly available.

Browser Support

  • Chrome: 121.
  • Edge: 121.
  • Firefox: 127.
  • Safari: 18.4.

Source

Light dismiss for <dialog>

One of the nice features of the Popover API is its light dismiss behavior. This behavior is now part of <dialog>, implemented in Chrome 134, with a new closedby attribute controlling the behavior.

Browser Support

  • Chrome: 134.
  • Edge: 134.
  • Firefox: not supported.
  • Safari: not supported.

The Web Locks API is now supported in shared storage

Chrome 134 integrates the Web Locks API into Shared Storage. This prevents scenarios such as where cross-site reach measurement can result in duplicate reporting, due to the potential race conditions within the get() and set() logic.

Beta browser releases

Beta browser versions give you a preview of things that will be in the next stable version of the browser. It's a great time to test new features, or removals, that could impact your site before the world gets that release. New betas are Firefox 137 and Chrome 135. These releases bring many great features to the platform. Check out the release notes for all of the details. Here are just a few highlights.

Firefox 137 includes the Math.sumPrecise static method, which returns the sum of an Iterable (such as an Array). This release also includes Atomics.pause(). This method provides a hint to the CPU that the current thread is in a spinlock while waiting on access to a shared resource.

Chrome 135 includes a number of CSS features related to creating carousels. It also includes customizable <select> elements, and the command and commandfor attributes.