The open call for Interop 2027 runs from early September to late September 2026, and proposals must be based on mature standards and be verifiable through Web Platform Tests.

Proposals can be filed as new GitHub issues or by supporting existing ones, with a preference for strengthening current issues over creating duplicates.

Interop 2026 focused on CSS features and technologies like the Navigation API, View Transitions, WebRTC, and WebTransport, with proposals drawn from the development community.

Developers should consult the Interop Proposers Guide for submission guidelines and expectations.

Progress in Interop 2025 showed a dramatic increase in test pass rates across browsers, rising from 29% to 97% thanks to collaborative efforts.

Apple’s WebKit team is inviting developers to submit ideas for Interop 2027, the annual cross-browser interoperability initiative.

Interop began in 2022, evolving from Compat, and now brings together major browser makers and organizations to tackle interoperability across web technologies.

A strong proposal should be specific, impactful, valuable, stable, and well-tested, with clear use cases and links to stable web standards and relevant Web Platform Tests coverage.