Cursor vs Claude vs Copilot Rules: What Actually Changes
A practical comparison of how rule files behave in Cursor, Claude Code, and GitHub Copilot.
The short answer
All three tools support project-level guidance, but they differ in consistency and control points.
Cursor strengths
Cursor applies `.cursorrules` tightly in editing workflows. Great for:
- code style and architecture constraints
- preferred libraries and anti-pattern bans
- refactor boundaries
Best when you want deterministic output in IDE-first work.
Claude Code strengths
`CLAUDE.md` is strong for deeper context, repo reasoning, and task planning. Great for:
- multi-step implementation plans
- migration/refactor constraints
- reasoning-heavy debugging workflows
Best when tasks span files, scripts, and architecture decisions.
Copilot strengths
`.github/copilot-instructions.md` is ideal for broad repo conventions and onboarding consistency. Great for:
- standards every contributor should inherit
- PR-friendly conventions across many repos
- alignment with GitHub-native workflows
Best for org-wide baseline behavior.
What teams miss
Do not assume the same prompt contract across tools. Maintain tool-specific examples and smoke tests so a policy update can be validated in each assistant.
Recommended setup
Use one canonical standards doc, then compile to each tool format. Keep a lightweight test suite of prompts and expected outputs so rule drift gets caught early.