HTTP Status Codes

Continue

The initial part of the request has been received and the client should continue.

Use — Sent with Expect: 100-continue while uploading a large body.

Switching Protocols

The requester asked the server to switch protocols and the server agreed.

Use — WebSocket upgrades and HTTP/2 or h2c negotiation.

Processing

The server has received and is processing the request, but no response is ready yet.

Use — WebDAV long-running uploads.

Early Hints

Preliminary headers are sent before the final response so the client can start preloading.

Use — Link preload headers for critical resources.

OK

The request succeeded. The response body depends on the method.

Use — Default success for GET, or a read from an API.

Created

The request succeeded and one or more new resources were created.

Use — POST that creates a user, order, or record.

Accepted

The request was accepted for processing but has not been completed.

Use — Queued background jobs and batch submissions.

Non-Authoritative Information

The response is a modified copy of what the origin server returned.

Use — Mirrors or proxies rewriting an upstream body.

No Content

The server successfully processed the request and returns no body.

Use — DELETE, and PUT with no returned representation.

Reset Content

Succeeded, but the client should reset the document view that caused the request.

Use — Clearing a form after a successful submit.

Partial Content

Only part of the resource is being delivered, per a Range header.

Use — Resumable downloads and media seeking.

Multi-Status

The body contains multiple independent status codes, not just one.

Use — WebDAV per-property results.

Already Reported

The members of a DAV binding have already been enumerated and are not repeated.

Use — WebDAV repeating a prior Propfind result.

IM Used

The server fulfilled the request and the response is the result of instance manipulations.

Use — Delta encoding in HTTP compression.

Multiple Choices

The request has more than one possible response and the client must pick one.

Use — Ambiguous resource selection.

Moved Permanently

The resource has a new permanent URL; update your links.

Use — Domain migrations and http to https.

Found

The resource lives temporarily at a different URL.

Use — Legacy short-link and login redirect flows.

See Other

The response to the request can be found at another URL using GET.

Use — Redirect after a form POST.

Not Modified

The cached copy is still fresh; no body is sent.

Use — Conditional GET with If-None-Match or If-Modified-Since.

Use Proxy

The resource must be accessed through the proxy given in the response.

Use — Legacy proxy redirection.

Switch Proxy

The request must be repeated at the URI given in the response, using a proxy.

Use — Reserved and rarely implemented. Most clients fall back to 302 behaviour.

Temporary Redirect

The request must be repeated at another URL, keeping the method and body.

Use — Preserving POST semantics across a temporary move.

Permanent Redirect

Like 307 but the move is permanent and cacheable.

Use — Permanent http to https enforcement.

Bad Request

The server cannot process the request because of a client syntax error.

Use — Malformed JSON, bad query parameters.

Unauthorized

Authentication is required and has failed or has not been provided.

Use — Missing or expired credentials; include WWW-Authenticate.

Payment Required

Reserved for future use, originally for digital payment schemes.

Use — Quota or billing walls; widely used by WebTorrent and paywalls.

Forbidden

The server understood the request but refuses to authorise it.

Use — Authenticated but not permitted, or WAF blocks.

Method Not Allowed

The method is known by the server but not supported for this resource.

Use — POST to a read-only endpoint; include Allow header.

Not Acceptable

No representation is available matching the Accept headers.

Use — Unsupported Accept-Encoding or media type.

Proxy Authentication Required

The client must authenticate with a proxy first.

Use — Corporate proxy login challenges.

Request Timeout

The server gave up waiting for the request to be sent.

Use — Slow or stalled uploads.

Conflict

The request conflicts with the current state of the resource.

Use — Version conflicts on PUT, duplicate unique keys.

Gone

The resource was deliberately removed and will not come back.

Use — Signals crawlers to drop an index, softer than 404.

Length Required

The server refuses the request without a Content-Length header.

Use — Chunked uploads rejected by strict servers.

Precondition Failed

A condition given in the request headers evaluated false.

Use — If-Match checks for optimistic concurrency.

Payload Too Large

The request body is larger than the server is willing to process.

Use — Upload size limits; body must be smaller than limits.

URI Too Long

The request target is longer than the server will interpret.

Use — Overlong query strings or URLs.

Unsupported Media Type

The body is in a format the endpoint does not accept.

Use — Sending JSON to a form-only endpoint.

Range Not Satisfiable

The requested range cannot be fulfilled.

Use — Resume offsets past the end of a file.

Expectation Failed

The Expect header expectation cannot be met.

Use — Expect: 100-continue rejected by the server.

I'm a Teapot

The server refuses to brew coffee because it is a teapot. A joke spec.

Use — Easter eggs and health checks for spec compliance.

Misdirected Request

The request was directed at a server unable to produce a response.

Use — A client reusing a connection for the wrong authority.

Unprocessable Entity

Syntax is fine but the instructions cannot be followed due to semantic errors.

Use — Field-level validation errors in JSON APIs.

Locked

The resource is locked.

Use — WebDAV locked files.

Failed Dependency

The request failed because it depended on another request that failed.

Use — WebDAV transactional batch failures.

Too Early

The server is unwilling to process a request that might be replayed.

Use — TLS 1.3 early data replay protection.

Upgrade Required

The client must switch to a different protocol.

Use — Send Upgrade and Upgrade-Insecure-Requests headers.

Precondition Required

The server requires the request to be conditional.

Use — If-Match to prevent lost updates.

Too Many Requests

The user has sent too many requests in a given amount of time.

Use — Rate limiting; pair with Retry-After.

Request Header Fields Too Large

The header fields are too large to process.

Use — Oversized cookies or bearer tokens.

Unavailable For Legal Reasons

Blocked as a consequence of a legal demand.

Use — Court orders and government takedowns.

Internal Server Error

The server hit an unexpected condition and cannot fulfil the request.

Use — Unhandled exception, the catch-all server bug.

Not Implemented

The server does not support the functionality required to fulfil the request.

Use — Unknown HTTP verb, or HTTP/1.0 talking to an HTTP/2-only server.

Bad Gateway

A server acting as gateway or proxy got an invalid response upstream.

Use — Upstream service down, nginx in front of a dead node.

Service Unavailable

The server is temporarily unable to handle the request.

Use — Maintenance windows, deploys, overloaded backends; include Retry-After.

Gateway Timeout

A gateway or proxy did not receive a timely response upstream.

Use — Upstream too slow, proxy read timeout.

HTTP Version Not Supported

The server does not support the HTTP protocol version used in the request.

Use — Rejecting an experimental protocol version.

Variant Also Negotiates

A misconfigured transparent proxy produced a circular reference.

Use — Rare proxy misconfiguration.

Insufficient Storage

The server cannot store the representation needed to complete the request.

Use — WebDAV quota exceeded.

Loop Detected

The server terminated an operation because it encountered an infinite loop.

Use — WebDAV recursive expansion.

Not Extended

Further extensions to the request are required for the server to fulfil it.

Use — Deprecated in practice; rare.

Network Authentication Required

The client must authenticate to gain network access.

Use — Captive portals and intercepting proxies.