CLAUDE.md vs AGENTS.md vs Cursor Rules

CLAUDE.md, AGENTS.md and Cursor rules all do the same job: they tell an AI coding tool how to work in your project. The difference is which tool reads which file. This guide shows the file each tool uses, how they compare, and how to keep one set of rules across Claude Code, Cursor, Codex, GitHub Copilot and Gemini CLI.

Quick answer: Claude Code reads CLAUDE.md, Codex reads AGENTS.md, Cursor reads .cursor/rules and also AGENTS.md, GitHub Copilot reads .github/copilot-instructions.md, and Gemini CLI reads GEMINI.md. Keep your shared rules in AGENTS.md and point the other files at it.

CLAUDE.md

CLAUDE.md is the project guide Claude Code loads at the start of every session. It can live at the project root, in ~/.claude for personal rules, and in subfolders. It supports imports, so a line like @AGENTS.md pulls in your shared rules. Create one with the free CLAUDE.md generator.

AGENTS.md

AGENTS.md is an open format read by Codex and a growing list of agents, including Cursor. Agents use the AGENTS.md closest to the file they are editing, so a monorepo can have one per package. Because so many tools read it, it is the best home for rules you want everywhere. Start from the free AGENTS.md generator.

Cursor rules

Cursor project rules are .mdc files in .cursor/rules, each with a small header that says when it applies: always, for matching files, when relevant, or manually. The older single .cursorrules file still works but project rules are recommended. Generate one with the free Cursor rules generator.

copilot-instructions.md and GEMINI.md

GitHub Copilot reads .github/copilot-instructions.md for every chat and agent request in the repository, with optional path-specific files in .github/instructions. Gemini CLI reads GEMINI.md files from your home folder, the project and subfolders, and can be set to read AGENTS.md instead. Use the free copilot-instructions.md generator and GEMINI.md generator.

How to keep one set of rules for every tool

1. Put the shared rules, commands, code style and design rules, in AGENTS.md.

2. In CLAUDE.md, import it with @AGENTS.md and add only Claude-specific notes.

3. Cursor reads AGENTS.md already; add .cursor/rules only for rules scoped to certain folders.

4. For Copilot and Gemini CLI, point their files at AGENTS.md or keep a short copy in sync.

The rules matter less than the design they point to. Every file should name one design source, a template saved in your repo, so each tool builds pages that look like one product. Read more on Claude Code skills vs hooks vs subagents.