Mã trạng thái HTTP & MIME Types

Continue

Request headers accepted — client may send the body.

Switching Protocols

Server agrees to switch protocol (e.g. HTTP → WebSocket upgrade).

Processing

WebDAV: request received, still working — prevents client timeout.

Early Hints

Preload hints sent before the final response, so browsers fetch assets sooner.

OK

Standard success — the response body carries the result.

Created

Resource created; Location header usually points to it.

Accepted

Request queued for async processing — no promise it will finish.

No Content

Success with an intentionally empty body (common for DELETE/PUT).

Partial Content

Byte-range response — used by video streaming and resumable downloads.

Moved Permanently

Permanent redirect; browsers and search engines update their references.

Found

Temporary redirect; method may change to GET on follow.

Not Modified

Cached copy is still valid — sent for conditional requests (ETag / If-Modified-Since).

Temporary Redirect

Like 302 but the method and body must not change.

Permanent Redirect

Like 301 but the method and body must not change.

Bad Request

Malformed request — syntax, framing, or invalid parameters.

Unauthorized

Authentication missing or invalid — really means "unauthenticated".

Forbidden

Authenticated but not allowed — credentials won’t help.

Not Found

No resource at this URL (or the server hides its existence).

Method Not Allowed

URL exists but not for this HTTP method — check the Allow header.

Not Acceptable

Server cannot produce a representation matching the Accept headers.

Request Timeout

Client took too long to send the full request.

Conflict

Request clashes with current resource state (e.g. concurrent edit).

Gone

Deliberately removed, permanently — stronger signal than 404.

Length Required

Server insists on a Content-Length header.

Precondition Failed

An If-* conditional header did not match (optimistic locking).

Content Too Large

Request body exceeds the server’s size limit.

Unsupported Media Type

Body format not supported (wrong Content-Type).

I'm a teapot

April-fools RFC 2324; some APIs use it for playful blocks.

Unprocessable Content

Syntax is fine but the data fails validation rules.

Too Early

Server refuses to risk a replayed request (TLS early data).

Too Many Requests

Rate limit hit — Retry-After tells you when to try again.

Request Header Fields Too Large

Headers (often cookies) exceed the server limit.

Unavailable For Legal Reasons

Blocked for legal/censorship reasons.

Internal Server Error

Unhandled server-side failure — the catch-all 5xx.

Not Implemented

Server does not support this method at all.

Bad Gateway

Proxy/load balancer got an invalid response from the upstream server.

Service Unavailable

Temporarily overloaded or down for maintenance — retry later.

Gateway Timeout

Proxy gave up waiting for the upstream server.

HTTP Version Not Supported

Requested HTTP version is not supported.

Insufficient Storage

WebDAV: server cannot store what the request requires.

Loop Detected

WebDAV: infinite loop while processing the request.