HTTP Status Codes Reference
Complete reference for all HTTP status codes with explanations. Look up any status code quickly.
About this reference
A searchable reference of HTTP status codes, from 100 Continue to 511 Network Authentication Required, each with a short explanation. Type in the search box to filter.
Knowing the first digit tells you the class: 1xx informational, 2xx success, 3xx redirect, 4xx client error and 5xx server error.
How to use it
- Type a code or word in the search box.
- Read the matching codes and explanations.
The five classes
1xx informational. 2xx success (200 OK, 201 Created, 204 No Content). 3xx redirection (301 Moved Permanently, 302 Found, 304 Not Modified). 4xx client error (400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found, 429 Too Many Requests). 5xx server error (500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout).
Worked example
Most-seen codes
| 200 | OK |
| 301 | Moved permanently (use for SEO redirects) |
| 404 | Not found |
| 500 | Server error |
| 503 | Service unavailable (temporary) |
Tips and common mistakes
- Use 301 for permanent moves and 302 or 307 for temporary ones.
- Return real 404 codes for missing pages, not 200 with an error message (a soft 404).
- 401 means not authenticated; 403 means authenticated but not allowed.
- Use 503 with Retry-After during maintenance.
- 429 tells clients to slow down.
Frequently asked questions
What does a 404 error mean?
The server cannot find the requested page.
What is the difference between 301 and 302?
301 is permanent; 302 is temporary.
What does 500 mean?
An unexpected error on the server.
What is the difference between 401 and 403?
401 means login required; 403 means access denied even if logged in.
What is 418?
I'm a teapot, an April Fools' joke from 1998.
Which codes matter for SEO?
301, 404, 410 and 5xx.