HTTP Status Codes

100 Continue # request received, continue
101 Switching Protocols # switching to new protocol
102 Processing # request being processed
103 Early Hints # preload resources

200 OK # request succeeded
201 Created # resource created
202 Accepted # request accepted, processing
204 No Content # success, no response body
206 Partial Content # partial resource delivered

301 Moved Permanently # resource moved permanently
302 Found # temporary redirect
304 Not Modified # cached version still valid
307 Temporary Redirect # temp redirect, keep method
308 Permanent Redirect # permanent, keep method

400 Bad Request # invalid request syntax
401 Unauthorized # authentication required
403 Forbidden # no permission to access
404 Not Found # resource not found
405 Method Not Allowed # method not supported
429 Too Many Requests # rate limit exceeded

500 Internal Server Error # generic server error
501 Not Implemented # functionality not supported
502 Bad Gateway # invalid upstream response
503 Service Unavailable # server temporarily unavailable
504 Gateway Timeout # upstream server timeout