Claude Code Skills vs Cursor Rules vs Codex Skills
All three major AI coding tools let you customize agent behavior, but they do it differently. Here's how SKILL.md skills, .cursorrules, and Codex skills compare.
Quick Answer: Claude Code Skills and Codex Skills both use the SKILL.md open standard: one portable file with YAML frontmatter that also runs in Cursor, OpenCode, and OpenClaw. Cursor Rules (
.cursorrules) is a Cursor-only always-on prompt at the repo root. If you want portability, write SKILL.md. If you want a single line "always do X in this repo" for Cursor only,.cursorrulesis fine.
Feature comparison
| Feature | SKILL.md (Claude Code / Codex) | .cursorrules |
|---|---|---|
| Portable across agents | Yes (20+ agents) | No, Cursor only |
| YAML frontmatter with triggers | Yes | No |
| Loaded on demand | Yes, by trigger | Always on |
| Versioned distribution | Yes, via marketplaces | No |
| Reference files | Yes | No |
| Package as zip / install | Yes | No |
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When to pick each
- SKILL.md: You want the same behavior in multiple agents, or you want to distribute the skill to your team, or you want to install skills from a marketplace like Agensi.
- .cursorrules: You want a one-file, always-on system prompt for a single Cursor repo, and you never plan to leave Cursor.
- Codex Skills: Same as SKILL.md. Codex Skills is SKILL.md, just marketed under OpenAI''s naming.
Three portable skills to try
All three run identically in Claude Code, Codex CLI, Cursor, OpenCode, and OpenClaw:
- code-reviewer. Free, 764 installs.
- git-commit-writer. Free, 232 installs.
- prompt-engineer. Free, 126 installs.
Format details in our SKILL.md format reference.