Interop 2024 brings more features to Baseline

Rachel Andrew

Published: January 22, 2025

As Interop 2024 draws to a close, this post looks back at the most successful year ever for the project. We ended with all experimental browsers reporting a score of 99, with the stable versions not far behind. This success means that a number of features are now Baseline Newly available.

All browsers with a score of 99.
Interop 2024 Dashboard (as of January 22, 2025)

More features to Baseline

For a feature to be Baseline Newly available, it needs to be interoperable. It's therefore no surprise that Interop 2024 helped a number of features over that line and into Baseline 2024.

Registered custom properties

The @property rule and CSS.registerProperty() static method became Baseline Newly available in July 2024.

The font-size-adjust property

The font-size-adjust CSS property preserves apparent text size, regardless of the font used, by scaling fonts to the same size with respect to a specific metric, such as x-height. This can help make fallback fonts look the same size. It became Baseline Newly available in July 2024.

The requestVideoFrameCallback() method for <video>

The requestVideoFrameCallback() method for <video> schedules a function that runs with the next video frame. It's similar to requestAnimationFrame(), but for video, and became Newly available in October 2024.

Scrollbar styling with scrollbar-width and scrollbar-gutter

The scrollbar-width CSS property sets the width of the scrollbar, and scrollbar-gutter reserves space for the scrollbar, preventing unwanted layout changes as the scrollbar appears and disappears. They became Baseline Newly available in December 2024.

The transition-behavior property

The transition-behavior: allow-discrete CSS declaration allows transitions for properties whose animation behavior is discrete. Such properties can't be interpolated and swap from their start value to the end value at 50%. This property became Baseline Newly available in August 2024.

text-wrap: balance

The text-wrap CSS property sets how lines break in text that overflows the container. It is a shorthand for text-wrap-style and text-wrap-mode. The balance value lets you create balanced headlines and other short pieces of text. The text-wrap property became Baseline Newly available in March 2024.

Popover

Popover lets you create overlays declaratively using HTML, or with the showPopover() method. It almost made it to Baseline Newly available, and in fact we initially thought it had, however an issue with the Safari implementation meant that it didn't quite hit Newly available in 2024. The good news is that the issue is fixed in the current Safari Beta 18.3, so we'll soon be able to properly announce Popover as Baseline Newly available.

Fixes to Baseline features

There were features included in Interop 2024 that were already classed as Baseline Newly available, the work was to fix some small differences in implementation. These might be things that very few people run into, however small things make a big difference if it's you running into them.

CSS nesting

CSS nesting allows for shorter selectors, easier reading, and more modularity by nesting rules inside others. It became Baseline Newly available in December 2023, and was included in Interop 2024 to fix some outstanding interop issues.

Declarative Shadow DOM

The shadowrootmode attribute on <template> creates a shadow root without the use of JavaScript. It is a declarative alternative to the `attachShadow() method.

Interop 2025 is coming soon

The proposals are being finalized right now for Interop 2025, and we're excited to build on all of our success this year. Look out for the announcement in February to find out what's included. To follow along with things landing in Baseline, check out our series of Baseline Newly available features here on web.dev.