Interoperability matters because it ensures that the code you write for the web will work the same way for your users regardless of browser and device. The Interop project is a yearly effort where browser implementers survey developers about top pain-points and agree on areas where we will concentrate resources to drive to full interoperability.
Over the past four years, Interop has highlighted areas where bugs in engines prevented widespread adoption of important features, from CSS styling and layout to new HTML elements and web APIs. In 2024, Interop helped resolve important issues in multiple areas, including:
- The Popover API, which allows you to display content on top of other page content declaratively using HTML, is now fully supported across all browsers.
- Declarative shadow DOM, which lets you create shadow roots directly in HTML, by using the
<template>element, is now also fully supported and implementation quality across browsers has been improved. - CSS nesting, which lets you write shorter selectors, by nesting rules within other rules, now works the same across all browsers and allows for a “relaxed” syntax that matches what you might have experienced with CSS pre-processors.
- The way that browsers compute the accessible names and roles of the elements on the page is now consistent, improving the experience of assistive technology users.
Interop 2025 brings about an ambitious list of focus areas for this year’s Interop project, and we are looking forward to a successful collaboration. As with prior years, many proposals were submitted, and we received a lot of input and comments on them. Thank you for the time you spent telling us about how the web platform could be better for your use cases! Your feedback was key in helping focus our efforts on the areas where we can make a positive impact.
The areas that all browsers agreed to focus on in 2025 include:
- CSS anchor positioning, to place elements based on the position of other elements.
- View Transitions, to create animated visual transitions between different states of a document.
- Navigation API, to initiate, intercept, and modify browser navigation actions, making it easier for applications to manage user state changes.
backdrop-filter, to apply graphical effects such as blurring or color shifting to the area behind an element.- JSON module scripts, to make it easy to import JSON data in JavaScript modules.
- Core Web Vitals LCP and INP metrics, to measure the user experience quality of your site.
- Storage Access API, to help remove third-party cookies while still supporting user authentication flows.
- Layout, to continue improving the implementation quality of two fundamental primitives of the web: Grid and Flexbox.
- Pointer and mouse events
- Legacy mutation events removal
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- WebAssembly
- Web Compat
- WebRTC
- Writing modes
For more details on the above focus areas, see the full description on the Interop GitHub repository. And, if you want to follow the progress of the project over the course of the year, check out the Interop 2025 dashboard.
However, we want to acknowledge that we also hear frustration from developers that some long-lived interoperability concerns are still outstanding, and that the process for choosing focus areas in the Interop project is opaque. We are committed to providing better visibility into these ongoing interoperability gaps.
Last year, Edge launched a supplementary Top Developer Needs dashboard to fill this visibility gap and track the improvements made to address these long-lived issues. Some of the top issues we’re tracking, such as scroll-driven animations and anchor positioning, were addressed in 2024 and late-breaking progress on View Transitions also helped set the stage for Interop 2025. We will be updating this dashboard in the coming weeks and will continue to lobby within the Interop group for increased transparency and an end to confidential vetoes.
We’re excited about the improvements that the Interop project will bring about this year, and we thank you again for submitting proposals and sharing your input. These proposals, as well as other developer signals, such as surveys, help us understand what’s important to you.
