Google's Chrome team has released version 1.0 of Modern Web Guidance, a set of skills that feeds web development best practices and browser compatibility data to AI coding agents before they write code. With the stable release, the project is now maintained by the Google Chrome, Microsoft Edge, Mozilla Firefox and MDN teams, according to release notes published on GitHub on Nov. 10.
The project targets a gap that Chrome describes in its announcement post. Frontier coding models "can usually produce something that works," the team wrote, but a web development expert reviewing that code can almost always still find ways to improve it.
What ships in 1.0
According to the release notes, version 1.0 contains 203 use-case guides covering 250 web platform features. Each guide carries Baseline compatibility data, so an agent can pick a feature that fits the browsers a project has to support and add fallbacks where needed.
Chrome says every guide now gets sign-off from a technical lead in its subject area. Guides for user-facing features also went through a dedicated accessibility review, with testing on real assistive technologies by experts who rely on them every day.
Chrome says the skill works by having the agent call a command-line tool that searches the guide database and pulls in only the guides that match the task. Search now runs offline on a small embedding model combined with keyword ranking instead of TensorFlow.js, which cut the npm download from 23.5 MB to 8.8 MB, the release notes say.
Chrome also published a public dashboard with per-agent and per-guide evaluation results comparing agents with and without the guidance.
Where models fall short
Chrome's evaluations found recurring weak spots in frontier models, the announcement says. In accessibility they include keyboard focus management and accessible form validation. In security they include safe HTML sanitization and passkey credential management.
A recap post from the Chrome team on Nov. 13 says even the latest frontier models fail around half of its modern web checks. The team says models also tend to reach for JavaScript libraries where a native HTML or CSS feature would do the same job with less code.
Version 1.0 adds a modernization scanner, legacy-scan, that statically detects old patterns in an existing codebase and maps each one to the guide with its modern replacement. The release notes say it covers roughly 20% of guides for now, the ones with deterministic rules. Chrome says it plans to add audits in which the agent reasons about the code directly.
Early results from companies
Chrome cited several companies that tested the guidance, and the figures below are the companies' own as reported by Chrome. Japanese publishing platform note inc. said a 180-run evaluation on its production code raised pass rates on modern web checks from 61% to 94%.
MetaMask runs the guidance as an automated reviewer on pull requests to its open source browser extension, using a three-line prompt. Over its first five weeks, the bot reviewed about 480 pull requests and commented on 64, and engineers fixed 43 of its findings, mostly accessibility and HTML problems that linters don't catch, according to Chrome.
WeTV, Tencent's international streaming service, added an agent to its build pipeline that pairs the guidance with Chrome DevTools for agents. Chrome says the agent now resolves 90% of failed performance checks on its own, cutting resolution time from four hours to 30 minutes.
How agents get it
Developers can install the skill with npx modern-web-guidance@latest install from a project folder. Chrome says it is also available through the plugin marketplaces of coding tools including Claude Code, Codex, Cursor, Antigravity, Copilot, WebStorm, Kimi Code and Grok Build.
Chrome recommends pairing the guidance with Chrome DevTools for agents. In Chrome's framing, the guidance shapes the code an agent writes, and DevTools lets the agent run that code and check that it behaves as intended.
Source: Chrome for Developers, “Modern Web Guidance 1.0: The web platform expertise your coding agent is missing”
Additional sources: GoogleChrome on GitHub, “Modern Web Guidance v1.0.0 release notes”; Chrome for Developers, “ICYMI: Modern Web Guidance is now stable”
