What are Cursor Rules, and how do you install one?

A Cursor Rule is a small file that teaches Cursor your project's own conventions, preferred libraries, naming, architecture, instead of letting it fall back on generic training knowledge. Today that means an .mdc file living in .cursor/rules/. Older projects sometimes still carry a single root .cursorrules file from before Cursor split rules into per-glob files; Cursor still reads it for backward compatibility, but new projects should use the .cursor/rules/ folder instead. This guide covers what's in an .mdc file and gets one installed.

What's actually in a rule file

Every .mdc file opens with frontmatter, description, globs, and alwaysApply, followed by the actual instructions. globs is what makes rules different from a plain prompt: it's a file pattern, so Cursor auto-attaches the rule only when you're editing a matching file, without you selecting anything by hand. A rule with globs: "*.tsx" and alwaysApply: false only kicks in while you're in a .tsx file; one with alwaysApply: true applies to every request regardless of what's open.

Before you start

You need the Cursor editor and a project open in it. Nothing else is required for most rules; a couple of installer-based collections also need a runtime like PHP, noted below.

Create the rules folder

mkdir -p .cursor/rules

Pick or write a rule

Awesome Cursor Rules is the reference catalog: 150+ individually maintained .mdc files organized by framework, language, and workflow, from Next.js and SvelteKit to Solidity and embedded firmware. Browse its README for the one matching your stack, then copy it in:

curl -o .cursor/rules/<name>.mdc \
  https://raw.githubusercontent.com/PatrickJS/awesome-cursorrules/main/rules/<name>.mdc

If security is the priority rather than a specific framework, Cursor AI Project Rules for Modern Development ships one dedicated .mdc file per OWASP Top 10 category, for PHP/Drupal, JavaScript/React/Vue, and Python, plus an interactive PHP installer that lets you pick a language or install by tag instead of copying files one at a time.

Checkpoint: confirm the file is actually inside .cursor/rules/ and ends in .mdc, and that the frontmatter's opening --- is the very first line of the file.

Reload and verify it attached

Reopen the project in Cursor, or reload the window if it was already open. Edit a file that matches the rule's globs and ask Cursor something related to what the rule covers.

Checkpoint: the suggestion should reflect the rule's convention, not just Cursor's generic default. If it doesn't, the rule likely didn't load at all rather than being ignored, so check the two things above before assuming Cursor is choosing to skip it.

Use rules day to day

Most rules need no manual invocation. Cursor attaches them automatically based on globs, or on every request if alwaysApply: true. You just keep working in the matching files; the convention shows up in suggestions without you asking for it.

If a rule doesn't seem to apply

Double check the globs pattern actually matches the file you're editing, a common miss is a glob scoped to src/**/*.ts in a project where the code actually lives in app/. If two rules disagree on the same file, tighten each one's globs so only the rule you want matches that file, rather than relying on Cursor to pick a winner between them.

Browse the full list at Cursor Rules for more, including stack-specific picks from the Awesome Cursor Rules catalog. The two named here aren't the end of the list either: this category keeps growing as more rule bundles get reviewed and added.