May 2026 Baseline: Newly available and widely available web features

In May 2026, a range of CSS features, event properties, and API additions became Baseline Newly available. At the same time, several units, interaction properties, and pseudo-classes reached Baseline Widely available status. Here is a rundown of the noteworthy updates.

State of CSS 2026 survey is open

The State of CSS 2026 survey is now accepting responses until July 1. This year's survey has been refined to emphasize features most relevant to developers working with AI-assisted tooling. Browser vendors use the results to guide engineering priorities and address common pain points.

Newly available in the core browser set

The following features now have support across the core browser set and are considered Baseline Newly available as of May 2026.

Container style queries

Container queries now extend beyond size constraints. Style queries let you apply styles to elements based on the custom properties of a parent container. This enables modular components that adapt their theme based on contextual placement without requiring complex class structures. See the MDN reference page for @container for details.

:open pseudo-class

Elements with open and closed states, such as <dialog> and <details>, previously required attribute checks or class management for styling. The :open pseudo-class matches these elements only when they are in their open state. Documentation is available on the MDN page for :open.

ToggleEvent.source

For work with the Popover API, the source property of the ToggleEvent interface returns the control element that triggered the popover toggle. This identifies the origin of the event, which helps coordinate complex UI interactions. Refer to the MDN documentation for ToggleEvent.source.

image-rendering property

The image-rendering CSS property controls the scaling algorithm used when resizing images. This is helpful for pixel art, low-resolution images, or QR codes, where sharp, pixelated scaling is preferable to blurry interpolation. See the MDN page for image-rendering.

text-decoration-skip-ink: all

The text-decoration-skip-ink property now supports an all value. While auto skips ink only at intersections, all forces the underline to skip all glyphs, providing finer typographic control. Details are in the MDN guide for text-decoration-skip-ink.

SharedWorker

The SharedWorker API is a background worker accessible from multiple browsing contexts like windows, tabs, or iframes on the same origin. This supports shared state, connection management, and coordinated background tasks across tab boundaries. Check the MDN documentation for SharedWorker.

Widely available features

The following features are now broadly compatible and usable across projects.

lh and rlh length units

The lh unit corresponds to the computed line-height of the element on which it is used, making it easy to size elements like icon badges or background highlights to match a line of text. The rlh unit is similar, but represents the line-height of the root element (<html>). This helps establish consistent vertical rhythm across a page regardless of local overrides. Both are covered in the MDN reference for length units.

Many web APIs require user interaction before they can fire, including video playback, popups, and clipboard access. The Navigator.userActivation property returns an object with the user's current and historical activation state on the window, letting scripts verify whether a user gesture occurred. See the MDN page for Navigator.userActivation.

clip-path

The clip-path property defines a clipping region that determines which parts of an element are visible. Using basic shapes or SVG paths, you can create layouts and transitions without relying on overflow hiding. Implementation details are on the MDN page for clip-path.

:user-invalid pseudo-class

Unlike :invalid, which applies styles immediately on page load, :user-invalid matches invalid form elements only after the user has interacted with them. This enables validation feedback after the user leaves a field. Learn more in the MDN documentation for :user-invalid.

Feedback and corrections

If any Baseline-related feature was missed, it can be captured in a future digest. Questions or feedback on Baseline can be filed in the issue tracker.