Status code atlas: choosing the right response

The request body may be sent; the final response is still pending.

An HTTP/1.1 protocol switch was accepted; consider a classic WebSocket upgrade.

A WebDAV-related processing indication, not the final success.

Resource hints arrive before the final response, without guaranteeing its outcome.

A temporary resumable-upload registration; check its current registry validity.

The entry checked on 2 October 2026 expires on 13 November 2026. Do not treat experimental support or that date as permanent; check the current IANA registry.

The request was handled successfully; content meaning depends on the method.

A resource was created; Location or the target URI identifies the primary resource.

Work was accepted but is not complete and may eventually fail.

An intermediary transformed the representation; this does not simply mean untrustworthy data.

The operation succeeded without content; do not parse a JSON body.

The operation succeeded and the initiating document view should reset. No content is sent.

One or more byte ranges were returned, with appropriate range metadata.

A WebDAV multi-resource result; the body can contain individual statuses.

Previously reported binding information is not repeated in its WebDAV context.

A specialised response to GET using supported instance manipulation, such as delta encoding.

Alternative representations exist and client selection may be needed.

A permanent new URI; consider historical POST-to-GET behaviour and caching.

A temporary alternative URI; do not assume every client preserves the method.

Retrieve the result from another resource with GET/HEAD, commonly after forms.

Validation of a conditional GET/HEAD; reuse the cached representation without new content.

A deprecated historical proxy redirect; do not use it in a new API design.

An unused reserved entry; do not choose it as an application response.

A temporary redirect preserving method and body.

A permanent redirect preserving method and body.

Malformed syntax or a general invalid request; safely explain what can be corrected.

Usable authentication credentials are required; include a WWW-Authenticate challenge.

Reserved for future use; do not present it as a universal payment contract.

The server understood but refuses; insufficient permission with valid identity is a common case.

The resource is unavailable or its existence is not disclosed, including access concealment.

The resource does not permit this method; communicate allowed methods with Allow.

No acceptable response representation can be supplied; inspect Accept preferences.

A forward proxy requires credentials; include Proxy-Authenticate.

The server did not receive the request in time; this is not every client timeout.

The request conflicts with resource state; correction or merging may be needed.

The resource’s availability is known to have permanently ended.

The request is refused without the required Content-Length information.

A supplied precondition failed; a stale If-Match is a typical example.

Supplied content exceeds a size limit; revise the payload or upload strategy.

The URI is too long; redesign oversized query or filter contracts.

The supplied content type or coding is unsupported; this differs from 406.

The requested range cannot be satisfied for the current representation; inspect its length.

The expectation in Expect cannot be met by the server chain.

Unused in IANA/RFC 9110; historical teapot humour is not a normal API contract.

The request reached a server unable to respond for that target.

Content is understood but its instructions cannot be processed; use a consistent validation contract.

A WebDAV resource is locked; this is not a generic account-lockout code.

A WebDAV action failed because a dependent action failed.

The server is unwilling to process early data with potential replay risk.

A protocol upgrade is required; consider the Upgrade information.

A conditional request is required; this is missing a precondition, not failing one.

A rate limit was exceeded; consider its scope and any Retry-After information.

An individual field or total header set is too large; inspect oversized cookies too.

Access is restricted for legal reasons, rather than an authentication failure.

An unexpected server condition; correlate internal logs without disclosing secrets.

Required functionality is not implemented; this differs from a resource’s 405 method rule.

A gateway received an invalid upstream response; identify the responding hop.

Temporary overload or maintenance may apply; Retry-After does not guarantee safe replay.

A gateway did not receive an upstream response in time; side effects may already exist.

The required HTTP version is not supported by the server.

A specialised configuration error in transparent content negotiation.

Insufficient storage for the operation in its WebDAV context; an extension code.

A loop occurred in a WebDAV operation; not a generic redirect-loop status.

An obsolete historical extension entry; do not use it for a new API.

Network or captive-portal access requires authentication; not ordinary application login.