How to use the HTTP Status Codes Reference
- Search by number or keyword.
- Filter by class with the chips.
- Read the meaning and fix accordingly.
About this tool
Every HTTP response starts with a three-digit status code. The first digit tells you the class: 2xx success, 3xx redirect, 4xx the client did something wrong, 5xx the server failed. Knowing the difference between, say, 401 and 403, or 301 and 302, saves hours of debugging and protects your search rankings.
SEO-critical codes
- 301/308 — permanent moves; search engines transfer ranking signals.
- 302/307 — temporary; the original URL stays indexed.
- 404 vs 410 — 410 tells crawlers to drop a page faster.
- 503 — with Retry-After, the right way to signal maintenance without losing rankings.
Frequently asked questions
401 vs 403?
401: you're not authenticated. 403: you are, but you're not allowed.
Should a missing page return 200?
No — a 'soft 404' confuses search engines. Return a real 404 status.