Interop 2026: Continuing to improve the web for developers

Rachel Andrew

Published: February 12, 2026

We're excited to announce Interop 2026, an effort to increase the interoperability of key features of the web platform across browsers. Run by a team of representatives from companies that make substantial contributions to browser rendering engines—including Apple, Google, Igalia, Microsoft, and Mozilla—Interop 2026 focuses on features that are high-priority for web developers and end users.

Consistent with earlier Interop efforts, selected tests will be continuously run on automated testing infrastructure, with pass rates displayed on the Interop 2026 dashboard.

Focus Areas

The focus areas for 2026 include several areas identified as top interop issues in the State of HTML and State of CSS surveys. We track these issues on webstatus.dev. Many features included this year also appear in the top 20 requested issues in the developer signals repository.

Anchor positioning

Appears in: Top interop issues, developer signals anchor positioning

Anchor positioning lets you place an element based on the position of another element, such as placing a tooltip next to the content it references. This focus area continues from Interop 2025 and includes only the tests from 2025.

Container style queries

Appears in: Top interop issues, developer signals container style queries

Container style queries apply styles to an element based on the computed values of custom properties of its container, using the @container at-rule together with one or more style() functions.

Dialogs and popovers

Appears in: Top interop issues, developer signals closedby, hint

For Interop 2026, work on the <dialog> element and Popover API focuses on:

  • The <dialog closedby> attribute, which sets the user actions that close a dialog (for example, clicking outside the dialog).
  • The :open CSS pseudo-class, which matches elements that have open states.
  • The popover="hint" global attribute, which creates a popover subordinate to other auto popovers, useful for tooltips.

Scroll-driven animations

Appears in: Top interop issues

This includes the animation-timeline, scroll-timeline, and view-timeline CSS properties, which advance animations based on the user's scroll position.

View transitions

Appears in: Top interop issues, developer signals Cross-document view transitions

Interop 2025 brought same-document view transitions to Baseline Newly available. For Interop 2026, the view transitions work focuses on:

  • Improving same-document view transitions.
  • The blocking="render" attribute for <link>, <script>, and <style>.
  • The <link rel="expect"> attribute.
  • The :active-view-transition-type() CSS pseudo-class.
  • Cross-document view transitions.

The attr() CSS function

Appears in developer signals attr()

The attr() CSS function returns the value of an attribute of an HTML element, with the option to return that value as a specific type or with a specific unit.

As well as these key features highlighted by you in the surveys, Interop 2026 includes:

The contrast-color() CSS function

The contrast-color() CSS function selects a color that has guaranteed contrast against a specified foreground or background color.

Custom highlights

Custom highlights let you style arbitrary text ranges without adding extra elements to the DOM.

Fetch uploads and ranges

Work on the fetch() method focuses on ReadableStream in the body to stream data to the server, supporting FormData and media types for requests and responses, and supporting the Range header.

IndexedDB

The IndexedDB focus area targets the getAllRecords() methods of IDBObjectStore and IDBIndex. These methods speed up read operations on large datasets by returning records and their primary keys in batches.

JSPI for Wasm

The JavaScript Promise Integration API (JSPI) lets Wasm applications that expect synchronous access to external functionality work in an environment where that functionality is asynchronous.

Media pseudo-classes

This area includes the :playing, :paused, :seeking, :buffering, :stalled, :muted, and :volume-locked CSS pseudo-classes, which match <audio> and <video> elements based on their state.

This year, the work will focus on continuing to improve the interoperability of the Navigation API, and on the precommitHandler option to navigateEvent.intercept(), which defers the commit until a handler has resolved.

Scoped custom element registries

The CustomElementRegistry() constructor creates a new custom element registry separate from the global one, letting multiple custom elements with the same tag name coexist.

Scroll snap

This focus area covers CSS scroll snap, which controls panning and scrolling behavior within a scroll container.

The shape() CSS function

The shape() CSS function creates shapes using commands like line, move, and curve, and can be used with clip-path and shape-outside.

Web compat

This area targets specific interoperability issues that cause real-world problems, including:

  • ESM module loading.
  • The timing of scroll events relative to animation events.
  • Unprefixing the -webkit-user-select property.

WebRTC

For Interop 2026, work focuses on fixing the remaining failing tests from the Interop 2025 focus area and continuing to improve WebRTC interoperability.

The WebTransport API

This area covers the WebTransport API, which transmits data between a client and server using the HTTP/3 protocol.

The zoom CSS property

Continuing from Interop 2025, this area focuses on the zoom CSS property, which scales the size of an element and affects page layout.

Investigation efforts

Interop 2026 also includes investigation efforts to prepare future features for testing and interoperability work:

  • Accessibility testing: Working to generate consistent accessibility trees across browsers and improving WPT infrastructure.
  • JPEG XL: Focusing on making the JPEG XL image format testable, including defining requirements for progressive rendering.
  • Mobile testing: Improving WPT infrastructure to test mobile-specific features like dynamic viewport changes.
  • WebVTT: Fixing tests and updating documentation to improve understanding of standard conformance.

Track progress through 2026

Follow along with the project on the Interop 2026 dashboard.

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