How to use this HTTP status code reference
- Type a code such as
429or a word such as redirect, cache or timeout to filter the list instantly. - Use the 1xx to 5xx buttons to show a single class of responses.
- Each card explains what the code means in practice and which headers usually go with it.
The five classes of status codes
- 1xx Informational: interim responses while a request continues, such as 101 for WebSocket upgrades.
- 2xx Success: the request worked. 200 is the default, 201 means something was created, 204 means success with no body.
- 3xx Redirection: the client must go elsewhere. 301 and 308 are permanent; 302, 303 and 307 are temporary; 304 means "use your cached copy".
- 4xx Client errors: the request was wrong. 400 for bad input, 401 for missing login, 403 for no permission, 404 for a missing page, 429 for rate limits.
- 5xx Server errors: the server failed. 500 is a crash, 502 and 504 point to a proxy or upstream problem, 503 means temporarily unavailable.
Status codes and SEO
Search engines read status codes carefully. Use 301 or 308 when a page moves for good, so its ranking passes to the new URL. Use 404 or 410 for removed pages rather than redirecting everything to the home page, which Google treats as a "soft 404". Return 503 with a Retry-After header during maintenance so pages are not dropped from the index. Many 5xx errors cause crawlers to slow down.
What is the difference between 401 and 403?
401 means you are not authenticated: log in or send a valid token. 403 means you are authenticated but not allowed to access the resource.
Should I use 301 or 302 for a redirect?
Use 301 (or 308) when the move is permanent, such as a new domain or URL structure. Use 302 (or 307) for temporary moves, like a sale page or A/B test.
What does 502 Bad Gateway mean?
A proxy, CDN or load balancer reached your application server but got an invalid response, usually because the app crashed, restarted or is not listening on the expected port.