HTTP Status Code Reference

Signification : Request headers received, continue body.

Quand utiliser : Expect: 100-continue flows.

Causes fréquentes : Large upload handshakes.

Exemple : Client sends headers first for a large upload.

Signification : Server switches protocols.

Quand utiliser : WebSocket upgrade accepted.

Causes fréquentes : Upgrade header negotiation.

Exemple : HTTP connection upgraded to WebSocket.

Signification : Server is processing long request.

Quand utiliser : WebDAV operations.

Causes fréquentes : Long-running write operations.

Exemple : Server confirms it is still working.

Signification : Preload resources before final response.

Quand utiliser : Performance optimization.

Causes fréquentes : Server sends Link preload hints.

Exemple : Browser starts downloading CSS early.

Signification : Request succeeded.

Quand utiliser : Normal successful GET/POST.

Causes fréquentes : Valid endpoint and payload.

Exemple : API returns requested user profile.

Signification : Resource created successfully.

Quand utiliser : POST creates resource.

Causes fréquentes : Create endpoints.

Exemple : Order created and ID returned.

Signification : Accepted for async processing.

Quand utiliser : Job queues/background tasks.

Causes fréquentes : Long task deferred.

Exemple : Video transcode job enqueued.

Signification : Returned metadata may be transformed.

Quand utiliser : Proxy modified response metadata.

Causes fréquentes : Intermediary transformations.

Exemple : Proxy returns transformed headers.

Signification : Success with no body.

Quand utiliser : DELETE/PUT with no response body.

Causes fréquentes : Successful update without payload.

Exemple : Settings updated successfully.

Signification : Client should reset form/view.

Quand utiliser : After form submission.

Causes fréquentes : Action completed and UI reset needed.

Exemple : Form save response asks UI to clear fields.

Signification : Partial range returned.

Quand utiliser : Range requests/download resumes.

Causes fréquentes : Streaming and resumable downloads.

Exemple : Video byte-range requested.

Signification : Multiple status values in one response.

Quand utiliser : WebDAV multi-resource responses.

Causes fréquentes : Batch operations.

Exemple : Some files copied, some failed.

Signification : Members already enumerated.

Quand utiliser : WebDAV propstat loops.

Causes fréquentes : Duplicate entries avoided.

Exemple : Depth traversal avoids repeats.

Signification : Instance manipulation applied.

Quand utiliser : Delta encoding responses.

Causes fréquentes : Advanced cache/delta systems.

Exemple : Server returns diff instead of full resource.

Signification : Multiple response options.

Quand utiliser : Content negotiation/manual choice.

Causes fréquentes : Resource has variants.

Exemple : User can pick language-specific resource.

Signification : Permanent redirect.

Quand utiliser : Canonical URL changes.

Causes fréquentes : Domain/path migrations.

Exemple : Old blog URL redirects to new URL.

Signification : Temporary redirect.

Quand utiliser : Short-term routing changes.

Causes fréquentes : Auth or temporary routing.

Exemple : Unauthenticated user redirected to login.

Signification : Redirect using GET.

Quand utiliser : After POST to avoid re-submit.

Causes fréquentes : PRG pattern.

Exemple : Form post then redirect to receipt page.

Signification : Use cached version.

Quand utiliser : ETag/If-Modified-Since cache validation.

Causes fréquentes : Client cache is fresh.

Exemple : Browser uses cached CSS file.

Signification : Deprecated proxy instruction.

Quand utiliser : Legacy only.

Causes fréquentes : Old systems.

Exemple : Rarely used today.

Signification : Reserved code.

Quand utiliser : Never in modern use.

Causes fréquentes : Historical placeholder.

Exemple : No practical usage.

Signification : Temporary redirect preserving method.

Quand utiliser : Temporary move without method change.

Causes fréquentes : Maintenance and temporary routing.

Exemple : POST remains POST after redirect.

Signification : Permanent redirect preserving method.

Quand utiliser : Permanent move with method safety.

Causes fréquentes : Modern permanent migrations.

Exemple : API endpoint moved permanently.

Signification : Malformed request.

Quand utiliser : Invalid syntax/params.

Causes fréquentes : JSON parse errors, missing fields.

Exemple : Invalid payload schema submitted.

Signification : Auth required or failed.

Quand utiliser : Missing/invalid credentials.

Causes fréquentes : Expired token.

Exemple : JWT missing in Authorization header.

Signification : Reserved for future payment use.

Quand utiliser : Custom paywall semantics.

Causes fréquentes : Subscription checks.

Exemple : Premium endpoint behind billing.

Signification : Authenticated but not allowed.

Quand utiliser : Permission denied.

Causes fréquentes : Role restrictions.

Exemple : Viewer tries admin action.

Signification : Resource not found.

Quand utiliser : Unknown endpoint/resource ID.

Causes fréquentes : Bad URL/ID deleted.

Exemple : User ID does not exist.

Signification : HTTP method not allowed here.

Quand utiliser : Endpoint exists but method invalid.

Causes fréquentes : GET on POST-only endpoint.

Exemple : DELETE sent to read-only route.

Signification : Cannot satisfy Accept header.

Quand utiliser : Content negotiation failure.

Causes fréquentes : Unsupported media type response.

Exemple : Client requests XML, server only JSON.

Signification : Proxy auth required.

Quand utiliser : Corporate proxy auth.

Causes fréquentes : Proxy challenge.

Exemple : Proxy asks for credentials.

Signification : Server timed out waiting.

Quand utiliser : Slow or stalled client request.

Causes fréquentes : Network latency/user aborts.

Exemple : Upload stalled before completion.

Signification : Request conflicts with current state.

Quand utiliser : Version conflicts/duplicates.

Causes fréquentes : Concurrency collisions.

Exemple : Attempt to create existing username.

Signification : Resource intentionally removed.

Quand utiliser : Permanent deletion with intent.

Causes fréquentes : Deprecated resources.

Exemple : Legacy API removed permanently.

Signification : Content-Length header required.

Quand utiliser : Server requires known body length.

Causes fréquentes : Chunked/unknown body sizes.

Exemple : Upload endpoint needs fixed length.

Signification : Conditional headers failed.

Quand utiliser : ETag/version preconditions.

Causes fréquentes : Stale resource version.

Exemple : If-Match does not match current ETag.

Signification : Request body too large.

Quand utiliser : File/JSON size limits exceeded.

Causes fréquentes : Upload limit exceeded.

Exemple : Image upload exceeds max MB.

Signification : Request URI too long.

Quand utiliser : Huge query strings.

Causes fréquentes : Misused GET with massive params.

Exemple : Search filters encoded in giant URL.

Signification : Request media type not supported.

Quand utiliser : Wrong Content-Type.

Causes fréquentes : text/plain sent instead of application/json.

Exemple : API expects JSON body.

Signification : Invalid byte range.

Quand utiliser : Bad range requests.

Causes fréquentes : Range beyond file length.

Exemple : Resume download offset too high.

Signification : Expect header unmet.

Quand utiliser : 100-continue expectations fail.

Causes fréquentes : Server doesn't support expectation.

Exemple : Client expected continue handshake.

Signification : RFC joke code; often used playfully.

Quand utiliser : Easter eggs/test responses.

Causes fréquentes : Custom humorous API responses.

Exemple : Tea endpoint refusing coffee.

Signification : Unofficial rate-limit style response.

Quand utiliser : Custom throttling.

Causes fréquentes : Client too aggressive.

Exemple : Legacy Twitter-style throttling.

Signification : Request sent to wrong server.

Quand utiliser : HTTP/2 connection reuse mismatch.

Causes fréquentes : TLS/SNI mismatch.

Exemple : Shared connection wrong authority.

Signification : Semantically invalid payload.

Quand utiliser : Validation errors.

Causes fréquentes : Field-level validation fails.

Exemple : Email format invalid in signup form.

Signification : Resource is locked.

Quand utiliser : WebDAV locking.

Causes fréquentes : Concurrent write lock.

Exemple : Document locked by another editor.

Signification : Dependent action failed.

Quand utiliser : Batch/transactional operations.

Causes fréquentes : Previous operation in chain failed.

Exemple : Move fails after lock step fails.

Signification : Server unwilling to process replay-risk request.

Quand utiliser : Early data replay protection.

Causes fréquentes : TLS early data concerns.

Exemple : Server asks client to retry safely.

Signification : Switch to newer protocol.

Quand utiliser : Require TLS/new HTTP version.

Causes fréquentes : Plain HTTP to HTTPS-only service.

Exemple : Server requires HTTPS upgrade.

Signification : Conditional request required.

Quand utiliser : Prevent lost updates.

Causes fréquentes : Missing If-Match/If-Unmodified-Since.

Exemple : Update endpoint requires version check.

Signification : Rate limit exceeded.

Quand utiliser : Throttle abusive/high-frequency clients.

Causes fréquentes : Burst traffic without backoff.

Exemple : Client exceeds 100 req/min.

Signification : Headers too large.

Quand utiliser : Cookie/header bloat.

Causes fréquentes : Oversized cookies.

Exemple : Huge cookie payload rejected.

Signification : Blocked by legal demand.

Quand utiliser : Geo/legal restrictions.

Causes fréquentes : Court/government takedown.

Exemple : Content blocked in specific region.

Signification : Generic server failure.

Quand utiliser : Unhandled exceptions.

Causes fréquentes : App bugs/null pointers.

Exemple : Unexpected runtime exception.

Signification : Server lacks requested functionality.

Quand utiliser : Method/feature unsupported.

Causes fréquentes : Endpoint stub not implemented.

Exemple : PATCH not supported by server.

Signification : Invalid upstream response.

Quand utiliser : Proxy/gateway issues.

Causes fréquentes : Upstream crash/timeouts.

Exemple : Nginx receives malformed upstream response.

Signification : Temporary server unavailability.

Quand utiliser : Maintenance/overload.

Causes fréquentes : Deployment or overload.

Exemple : App in maintenance mode.

Signification : Upstream timed out.

Quand utiliser : Proxy timeout waiting upstream.

Causes fréquentes : Slow database/downstream service.

Exemple : API gateway timeout after 30s.

Signification : HTTP version unsupported.

Quand utiliser : Client sends unsupported protocol.

Causes fréquentes : Old client/proxy mismatch.

Exemple : HTTP/0.9 style request rejected.

Signification : Content negotiation config error.

Quand utiliser : Server negotiation loops.

Causes fréquentes : Misconfigured variants.

Exemple : Negotiated variant points to itself.

Signification : Server storage exhausted.

Quand utiliser : WebDAV or storage-backed writes.

Causes fréquentes : Disk full/quota exceeded.

Exemple : Cannot save uploaded file.

Signification : Infinite loop detected.

Quand utiliser : WebDAV depth operations.

Causes fréquentes : Cyclic bindings.

Exemple : Traversal loop breaks operation.

Signification : Further extensions required.

Quand utiliser : Policy extension requirements.

Causes fréquentes : Missing extension declarations.

Exemple : Server expects additional extension info.

Signification : Network login required.

Quand utiliser : Captive portals.

Causes fréquentes : Public Wi-Fi auth gates.

Exemple : User must login to Wi-Fi portal.