Google Modern Web Guidance 1.0: better code from AI agents

Your AI coding agent learned the web from old Stack Overflow answers. Google wants to fix that. On November 10, the Chrome team shipped Modern Web Guidance 1.0, a free set of skills that feeds AI coding agents current web platform practice and browser support data. It works with Claude Code, OpenAI Codex, Cursor, GitHub Copilot and Google's own Antigravity. The pitch: fewer polyfills, fewer hand-rolled widgets, more native browser features that are faster and more accessible.

What actually happened

From the v1.0.0 release notes and Chrome's docs:

• 203 use-case guides covering 250 web platform features. Accordions, tabs, carousels, navbars, scroll-driven animations, install prompts. The agent pulls only the guide it needs into its context window.
• Out of preview. An early version shipped at Google I/O in May 2026. With 1.0, the project is run by the Chrome, Microsoft Edge, Mozilla Firefox and MDN teams together, not Google alone.
• Baseline-aware. Guides use Baseline browser compatibility data, so the agent knows what actually works across browsers today.
• A legacy scanner. npx modern-web-guidance@latest legacy-scan . finds old patterns in your codebase and maps each one to a modern replacement. Google says it covers roughly 20% of the guides today, the ones with fixed detection rules.
• Public evals. Google's numbers show Claude Code passing 94% of tasks with guidance versus 58% without, and Codex CLI going from 50% to 86%. Search Engine Journal notes guided runs were usually slower and used more tokens.
• License. Code is Apache-2.0, guide content is CC-BY 4.0. It sends anonymous telemetry unless you set DISABLE_TELEMETRY=1.

Install is one command: npx modern-web-guidance@latest install, or through your agent's plugin marketplace.

Why it matters for your business

If a freelancer or an agent built your storefront or booking site in the last year, a lot of that code was written from training data that predates current browser features. That shows up as heavy JavaScript bundles, custom dropdowns screen readers can't use, and a slow mobile checkout.

1. Run the scanner on what you have. It's free and read-only. You get a list of legacy patterns with the fix next to each one.
2. Install it where your agent writes code. A 36-point jump in pass rate is worth a few more tokens.
3. Don't treat it as a review. It covers 20% of patterns by rule. The rest still needs a person who knows what "accessible" means on your checkout.

Sources: Modern Web Guidance v1.0.0 release (GitHub), Chrome for Developers docs, Search Engine Journal.