HTTP status code lookup

How to use it

1. Type a full code to see its meaning, the RFC section that defines it and whether caches may store it by default.
2. Type one or two digits to list every code that starts with them, a class such as 5xx, or words such as redirect, cache or rate limit to search names and notes.
3. Use the class menu to narrow the list. The reference links open the defining RFC section at the RFC Editor.
4. A code that is not registered still has a class. Clients that do not recognize a code must treat it like the x00 code of its class, which the page states for unassigned codes.

Redirects: 301, 302, 303, 307 and 308

The five redirect codes differ on two questions: is the move permanent, and may the client change the method. For historical reasons browsers turn a POST into a GET when they follow 301 or 302, and RFC 9110 allows it. 307 and 308 were added to forbid that change, so they are the safe choice when an API redirects a POST, PUT or DELETE. 303 always means fetch the new location with GET, which is why it is the standard reply after a form submission.

Permanent codes (301 and 308) tell clients and search engines to update stored links, and both are heuristically cacheable, so a browser may remember the redirect without explicit cache headers. Use a temporary code while you are still testing a move.

401 versus 403, and 400 versus 422

A 401 means the request lacks valid credentials, and the server must say how to authenticate in a WWW-Authenticate header. A 403 means the server refuses even though it may know who you are; sending the same credentials again will not help. Many APIs return 404 instead of 403 to avoid revealing that a resource exists, which RFC 9110 permits.

A 400 is for requests the server cannot parse or will not process because of a client error. RFC 9110 moved 422 (formerly WebDAV only) into the core specification for requests whose syntax is fine but whose content fails validation, which is how many JSON APIs report field errors.

Examples

Select an example to load it into the tool.

• 404404Load
• All redirects3xxLoad
• Rate limitingrate limitLoad
• Unassigned 499499Load

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