5 .cursorrules That Actually Changed What Cursor Generates (React/Next.js)

Most .cursorrules don't actually change anything. I tested 30+ rules over a couple weeks — same prompt, with and without each rule, comparing the diff. "Use TypeScript." "Prefer functional components." The AI was gonna do that anyway. Only 5 rules changed the output every time, and they all target the same blind spot. If you're new to .cursorrules , it's a file in your project root that tells Cursor how to generate code. In theory. The test For each rule, I ran the same workflow: Prompt Cursor without the rule → save output Add the rule to .cursorrules Run the same prompt → save output Diff the two If the output didn't change, the rule got cut. These 5 survived. 1. error.tsx alongside every page Always create error.tsx alongside every page.tsx. error.tsx must be a client component that receives error and reset props. Display fallback UI with a retry button. I had "use error boundaries" at first and it did literally nothing. Cursor just ignored it. But when I changed it to specifically