A preview of CSS functions and corner‑shape syntax, currently supported in Chrome 155 and Edge 154.
INTEROP 2027 PUSHES NEAR-UNIVERSAL CSS FUNCTIONS AND CORNER-SHAPE
*Interop's 2027 roadmap could make CSS functions and corner‑shape features available across Chrome, Edge, Firefox, and Safari within a year. The push follows a track record of rapid adoption, as seen with subgrid reaching near‑100% support after its 2023 inclusion.*
The Interop project, a joint effort by Google, Apple, Microsoft, Mozilla, Igalia and Bocoup, has become the engine driving universal browser support for emerging web standards. Since its inception, any focus area added to Interop has typically hit near‑100% support across all major browsers within a single year, a pattern demonstrated by the rapid rollout of CSS Subgrid after its 2023 inclusion. As 2026 draws to a close, the team at Mozilla is already planning Interop 2027, using a new ranking system to let developers up‑vote the features they need most. Among the top‑voted items are CSS functions and the experimental corner‑shape property, both poised to reshape layout and design workflows if they make the Interop cut.
How Interop delivers near‑universal adoption
Interop’s success hinges on coordinated implementation across the four dominant browsers—Chrome, Edge, Firefox and Safari. When a feature is added, each vendor commits to a synchronized release schedule, compressing what used to be multi‑year gaps into a twelve‑month window. The subgrid rollout proved the model: after its 2023 addition, test pass rates in all browsers converged to the black “Interop” line, indicating near‑full compliance. This collaborative cadence reduces fragmentation, lowers development risk, and forces vendors to prioritize standards over proprietary extensions. The upcoming Interop 2027 will apply the same pressure to CSS functions and corner‑shape, promising the same rapid convergence.
Will CSS functions become a standard by 2027?
CSS functions are already supported in Chrome 155 and Edge 154, but remain absent in Firefox 157 and Safari 27 as of October 2026. The proposal introduces an @function rule that mirrors JavaScript syntax, allowing developers to define reusable calculations like linear‑gradient generators or polar‑to‑cartesian translators. Because Chromium browsers have a working implementation, the Interop ranking system suggests a high probability of inclusion in the 2027 cycle. If accepted, the coordinated push could bring the feature to all major browsers within a year, turning what now feels like science‑fiction into a daily tool for designers.
What does corner‑shape add beyond border‑radius?
The corner‑shape property expands the palette of corner geometries beyond the quarter‑circle produced by border‑radius. Supported in Chrome 155 and Edge 154, it is still missing from Firefox 157 and Safari 27. Options include squircle, bevel, notch and scoop, each altering the border‑box itself rather than relying on clip‑path or masks. This means outlines, borders and box‑shadows follow the new shape automatically. The author notes a personal preference for bevels in sci‑fi UI designs, while squircle offers Apple‑style smoothness. If Interop 2027 adopts corner‑shape, developers can expect consistent cross‑browser rendering of these advanced forms without workarounds.
What are the broader implications for the web ecosystem?
A successful Interop 2027 rollout would tighten the feedback loop between standards bodies and front‑end teams. Designers could write once, deploy everywhere, cutting time spent on polyfills and browser‑specific hacks. Faster adoption also pressures legacy browsers to catch up, reducing the long tail of unsupported sites. For the industry, the pattern reinforces a collaborative model where feature voting directly shapes the roadmap, aligning vendor incentives with developer demand. The net effect is a more resilient, feature‑rich web platform that can keep pace with the ambitions of modern UI design.
Frequently asked questions
Which browsers currently support CSS functions?
As of October 2026, CSS functions are supported in Chrome 155 and Edge 154, but not in Firefox 157 or Safari 27.
What is the corner‑shape property and where is it available?
Corner‑shape adds new corner geometries like squircle, bevel, notch and scoop, and is supported in Chrome 155 and Edge 154 while Firefox 157 and Safari 27 lack support.
How fast does Interop typically bring a new CSS feature to all browsers?
When a focus area is added to Interop, it often reaches near‑100% support across all major browsers within a year, as demonstrated by the subgrid rollout.
The clock is ticking toward Interop 2027, and the votes are already in. With Chrome and Edge already ahead, the onus now lies on Firefox and Safari to close the gap before the year’s end. Should the ranking system translate into coordinated releases, developers will gain two powerful tools—CSS functions and corner‑shape—without the usual fragmentation. The web stands on the brink of a new design era, driven by a proven collaborative engine that refuses to let standards lag behind imagination.
Sources: [Hacker News – The Future of CSS, https://www.joshwcomeau.com/css/interop-2027/]