Apple’s WebKit blog published a detailed post this week outlining the results of Interop 2025, an industry-wide project focused on improving cross-browser interoperability. The update highlights steady progress across major browser engines and points to a year where alignment mattered more than competition.
The Interop project brings together Apple, Bocoup, Google, Igalia, Microsoft, and Mozilla. The group works on shared problem areas that affect everyday web development. The goal stays simple. Developers should write code once and trust that it works across browsers.
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Apple described Interop 2025 as a year of convergence, both in effort and outcome. The project selected 19 focus areas and five investigation areas across CSS, JavaScript, Web APIs, performance, and platform health. At the start of the year, only 29 percent of the selected tests passed across all browsers. By the end of the year, that number reached 97 percent, with experimental versions of Chrome, Edge, Firefox, and Safari all hitting 99 percent.
In its post, Apple explained how those gains came together.
“Each year, the Interop project chooses its focus areas through a collaborative process with proposals, research into what web developers need, and debates about priorities,” Apple said. “The results show that commitment paid off. Safari made the largest jump of any browser this year, climbing from 43 to 99.”
That improvement mattered because it came from areas that required heavy engineering work inside WebKit. Apple noted that it pushed for tougher focus areas because they would make a real difference for developers.
Areas that stood out
Apple highlighted three focus areas that shaped Interop 2025 in a meaningful way.
Anchor positioning allows developers to place popovers, menus, and tooltips relative to any element using only CSS. The feature now works consistently across browsers, removing the need for JavaScript-based positioning libraries.
Same-document View Transitions enable smooth UI animations between states directly in the browser. Apple shipped support in Safari 18.0 and 18.2, and broader interoperability means developers can now rely on the feature without browser-specific fallbacks.
The Navigation API replaces older history-based methods with modern navigation handling for single-page apps. Apple shipped support in Safari 26.2 and emphasized that interoperability arrived early, which reduces long-term compatibility issues.
Broader progress across the platform
Beyond those highlights, Apple listed contributions across all 19 focus areas. These included CSS and UI features such as @scope, backdrop-filter, text-decoration, layout systems, and writing modes. API work covered areas like Storage Access API, URLPattern, WebRTC, WebAssembly, and the scrollend event. Investigation areas such as accessibility testing, mobile testing, and Gamepad API testing helped lay the groundwork for future cycles.
Apple closed by pointing to the broader trend shown in the Interop 2025 data. All browser engines invested heavily, and their scores converged at the top by year’s end. That shared progress, Apple said, is what allows the web to remain predictable, stable, and developer-friendly across platforms.
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