ApiSimul logo ApiSimul — the switchboard

HTTP Status Code Reference

Meaning, scenarios and mock rules for 60 codes · Updated 2026-10-18

Status codes are the contract between a client and a server, and the rarely-seen ones are exactly the ones worth practising. Each page below explains one code, lists the situations that trigger it, and shows a mock rule that returns it locally — the same rule fields the mock editor on this site uses.

Informational responses (1xx)
100 Continue101 Switching Protocols102 Processing103 Early Hints
Successful responses (2xx)
200 OK201 Created202 Accepted203 Non-Authoritative Information204 No Content205 Reset Content206 Partial Content208 Already Reported226 IM Used
Redirection messages (3xx)
300 Multiple Choices301 Moved Permanently302 Found303 See Other304 Not Modified307 Temporary Redirect308 Permanent Redirect
Client error responses (4xx)
400 Bad Request401 Unauthorized402 Payment Required403 Forbidden404 Not Found405 Method Not Allowed406 Not Acceptable407 Proxy Authentication Required408 Request Timeout409 Conflict410 Gone411 Length Required412 Precondition Failed413 Content Too Large414 URI Too Long415 Unsupported Media Type416 Range Not Satisfiable417 Expectation Failed418 I’m a teapot421 Misdirected Request422 Unprocessable Content423 Locked424 Failed Dependency425 Too Early426 Upgrade Required428 Precondition Required429 Too Many Requests431 Request Header Fields Too Large451 Unavailable For Legal Reasons
Server error responses (5xx)
500 Internal Server Error501 Not Implemented502 Bad Gateway503 Service Unavailable504 Gateway Timeout505 HTTP Version Not Supported506 Variant Also Negotiates507 Insufficient Storage508 Loop Detected510 Not Extended511 Network Authentication Required

Frequently asked questions

Which codes have their own page?
60 codes across the five classes, from 100 to 511. Each page gives the meaning, the situations that produce it, and a ready-to-paste mock rule for returning it locally.

Why mock status codes at all?
Client code paths for 429 rate limits, 404 misses or 500 failures are usually the least tested parts of an app, because real backends rarely produce them on demand. A local mock returns any status deterministically, with a controllable delay and body.

Ready to try them live? The ApiSimul mock server runs entirely in your browser — define a rule, send a request, watch the response.