Chrome, Edge, Mozilla ship Modern Web Guidance for AI agents

The browser makers have shipped a tool for AI.

Modern Web Guidance, from Google Chrome, Microsoft Edge, Mozilla Firefox and MDN, is "a set of skills that embed web platform expertise, best practices, and browser compatibility data directly into your coding agents," per the README. Installation is one line: `npx modern-web-guidance@latest install`.

Coverage runs to 250 modern web features and 203 real-world developer use cases, weighted toward the parts of the stack coding agents tend to botch: 140 CSS & layout features, 74 JavaScript & APIs features, 36 HTML & DOM features. A `legacy-scan` subcommand "scans a codebase for legacy patterns to modernize."

The README states the motivation plainly. "Coding agents often default to older patterns because LLM training data contains vast amounts of legacy code. This often leads them to generate bloated JavaScript for tasks that now have native, high-performance web platform solutions."

Governance is cross-vendor: the project is "stewarded by the Google Chrome, Microsoft Edge, Mozilla Firefox, and MDN teams, alongside the web development community." The README does not announce a version number, and publishes no benchmark comparing guided and unguided agent runs. It lands into a crowded week for coding-agent tooling on our tracker.