The final selections for Interop 2026 have been announced, and this year total nineteen focus areas, three cleanup areas, and four investigation areas. This annual cooperative campaign has brought a great deal of consistency and interoperability to the web since its beginnings in 2021, and this year looks set to continue that tradition.

The Interop 2025 results were outstanding, with the overall interoperability score of its focus areas climbing from 28 to 95 in the course of the year; this has further moved up to a score of 97 in the month since the end of 2025. We’re excited about the prospect of similar improvements in this year’s focus areas!

HTML

At the markup layer, there wasn’t one proposal that stood out, but rather a collection of a few proposals related to dialogs and popovers — not just the <dialog> element and the popover attribute, but also the :open pseudo-class in CSS. There were some things still missing in implementations, and others that weren’t handled consistently. The Interop team combined the proposals into a single HTML focus area.

CSS

As is often the case, the presentation layer got a lot of attention from proposers, which led to eleven focus areas rooted in CSS. These are:

• Advanced attr()
• Container style queries
• contrast-color() function
• Custom highlights
• Media pseudo-classes
• Scroll-driven animations
• Scroll snap
• shape() basic shape function
• Anchor positioning (carryover from 2025)
• View transitions (carryover from 2025)
• CSS zoom (carryover from 2025)

JavaScript

At the scripting layer, the Interop team chose these seven focus areas:

• Fetch uploads and ranges (combined three separate proposals into one focus area)
• IndexedDB
• JSPI for Wasm
• Navigation API
• Scoped custom element registries
• WebRTC
• WebTransport

Web compat(ibility)

While all of Interop can be considered a web compat effort, there are always a few areas where the amount of work to achieve full alignment is small, but worth taking on as official focus areas. Sometimes, this can mean getting clarification from relevant W3C working groups, or doing origin trials to make sure the change is sufficiently low-impact. This year, work will focus on web compatibility issues with:

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

Investigation areas

Each year, the Interop team chooses a small number of areas to investigate how to get the proposals into future Interop years. This is usually done for proposals that lack the tests, or the testing infrastructure, to qualify as official focus areas. The 2026 investigations will be:

• Accessibility testing
• JPEG XL tests
• Mobile testing
• WebVTT

If you’d like to read more about Interop 2026, see the articles published today by Apple, Google, Microsoft, and Mozilla.

Igalia is proud to once again be part of the Interop process, and to champion a few proposals that are particularly close to our interests. We look forward to seeing all the progress this year will bring.