HTTP Status Code Reference

Significado: Request headers received, continue body.

Cuándo usar: Expect: 100-continue flows.

Causas comunes: Large upload handshakes.

Ejemplo: Client sends headers first for a large upload.

Significado: Server switches protocols.

Cuándo usar: WebSocket upgrade accepted.

Causas comunes: Upgrade header negotiation.

Ejemplo: HTTP connection upgraded to WebSocket.

Significado: Server is processing long request.

Cuándo usar: WebDAV operations.

Causas comunes: Long-running write operations.

Ejemplo: Server confirms it is still working.

Significado: Preload resources before final response.

Cuándo usar: Performance optimization.

Causas comunes: Server sends Link preload hints.

Ejemplo: Browser starts downloading CSS early.

Significado: Request succeeded.

Cuándo usar: Normal successful GET/POST.

Causas comunes: Valid endpoint and payload.

Ejemplo: API returns requested user profile.

Significado: Resource created successfully.

Cuándo usar: POST creates resource.

Causas comunes: Create endpoints.

Ejemplo: Order created and ID returned.

Significado: Accepted for async processing.

Cuándo usar: Job queues/background tasks.

Causas comunes: Long task deferred.

Ejemplo: Video transcode job enqueued.

Significado: Returned metadata may be transformed.

Cuándo usar: Proxy modified response metadata.

Causas comunes: Intermediary transformations.

Ejemplo: Proxy returns transformed headers.

Significado: Success with no body.

Cuándo usar: DELETE/PUT with no response body.

Causas comunes: Successful update without payload.

Ejemplo: Settings updated successfully.

Significado: Client should reset form/view.

Cuándo usar: After form submission.

Causas comunes: Action completed and UI reset needed.

Ejemplo: Form save response asks UI to clear fields.

Significado: Partial range returned.

Cuándo usar: Range requests/download resumes.

Causas comunes: Streaming and resumable downloads.

Ejemplo: Video byte-range requested.

Significado: Multiple status values in one response.

Cuándo usar: WebDAV multi-resource responses.

Causas comunes: Batch operations.

Ejemplo: Some files copied, some failed.

Significado: Members already enumerated.

Cuándo usar: WebDAV propstat loops.

Causas comunes: Duplicate entries avoided.

Ejemplo: Depth traversal avoids repeats.

Significado: Instance manipulation applied.

Cuándo usar: Delta encoding responses.

Causas comunes: Advanced cache/delta systems.

Ejemplo: Server returns diff instead of full resource.

Significado: Multiple response options.

Cuándo usar: Content negotiation/manual choice.

Causas comunes: Resource has variants.

Ejemplo: User can pick language-specific resource.

Significado: Permanent redirect.

Cuándo usar: Canonical URL changes.

Causas comunes: Domain/path migrations.

Ejemplo: Old blog URL redirects to new URL.

Significado: Temporary redirect.

Cuándo usar: Short-term routing changes.

Causas comunes: Auth or temporary routing.

Ejemplo: Unauthenticated user redirected to login.

Significado: Redirect using GET.

Cuándo usar: After POST to avoid re-submit.

Causas comunes: PRG pattern.

Ejemplo: Form post then redirect to receipt page.

Significado: Use cached version.

Cuándo usar: ETag/If-Modified-Since cache validation.

Causas comunes: Client cache is fresh.

Ejemplo: Browser uses cached CSS file.

Significado: Deprecated proxy instruction.

Cuándo usar: Legacy only.

Causas comunes: Old systems.

Ejemplo: Rarely used today.

Significado: Reserved code.

Cuándo usar: Never in modern use.

Causas comunes: Historical placeholder.

Ejemplo: No practical usage.

Significado: Temporary redirect preserving method.

Cuándo usar: Temporary move without method change.

Causas comunes: Maintenance and temporary routing.

Ejemplo: POST remains POST after redirect.

Significado: Permanent redirect preserving method.

Cuándo usar: Permanent move with method safety.

Causas comunes: Modern permanent migrations.

Ejemplo: API endpoint moved permanently.

Significado: Malformed request.

Cuándo usar: Invalid syntax/params.

Causas comunes: JSON parse errors, missing fields.

Ejemplo: Invalid payload schema submitted.

Significado: Auth required or failed.

Cuándo usar: Missing/invalid credentials.

Causas comunes: Expired token.

Ejemplo: JWT missing in Authorization header.

Significado: Reserved for future payment use.

Cuándo usar: Custom paywall semantics.

Causas comunes: Subscription checks.

Ejemplo: Premium endpoint behind billing.

Significado: Authenticated but not allowed.

Cuándo usar: Permission denied.

Causas comunes: Role restrictions.

Ejemplo: Viewer tries admin action.

Significado: Resource not found.

Cuándo usar: Unknown endpoint/resource ID.

Causas comunes: Bad URL/ID deleted.

Ejemplo: User ID does not exist.

Significado: HTTP method not allowed here.

Cuándo usar: Endpoint exists but method invalid.

Causas comunes: GET on POST-only endpoint.

Ejemplo: DELETE sent to read-only route.

Significado: Cannot satisfy Accept header.

Cuándo usar: Content negotiation failure.

Causas comunes: Unsupported media type response.

Ejemplo: Client requests XML, server only JSON.

Significado: Proxy auth required.

Cuándo usar: Corporate proxy auth.

Causas comunes: Proxy challenge.

Ejemplo: Proxy asks for credentials.

Significado: Server timed out waiting.

Cuándo usar: Slow or stalled client request.

Causas comunes: Network latency/user aborts.

Ejemplo: Upload stalled before completion.

Significado: Request conflicts with current state.

Cuándo usar: Version conflicts/duplicates.

Causas comunes: Concurrency collisions.

Ejemplo: Attempt to create existing username.

Significado: Resource intentionally removed.

Cuándo usar: Permanent deletion with intent.

Causas comunes: Deprecated resources.

Ejemplo: Legacy API removed permanently.

Significado: Content-Length header required.

Cuándo usar: Server requires known body length.

Causas comunes: Chunked/unknown body sizes.

Ejemplo: Upload endpoint needs fixed length.

Significado: Conditional headers failed.

Cuándo usar: ETag/version preconditions.

Causas comunes: Stale resource version.

Ejemplo: If-Match does not match current ETag.

Significado: Request body too large.

Cuándo usar: File/JSON size limits exceeded.

Causas comunes: Upload limit exceeded.

Ejemplo: Image upload exceeds max MB.

Significado: Request URI too long.

Cuándo usar: Huge query strings.

Causas comunes: Misused GET with massive params.

Ejemplo: Search filters encoded in giant URL.

Significado: Request media type not supported.

Cuándo usar: Wrong Content-Type.

Causas comunes: text/plain sent instead of application/json.

Ejemplo: API expects JSON body.

Significado: Invalid byte range.

Cuándo usar: Bad range requests.

Causas comunes: Range beyond file length.

Ejemplo: Resume download offset too high.

Significado: Expect header unmet.

Cuándo usar: 100-continue expectations fail.

Causas comunes: Server doesn't support expectation.

Ejemplo: Client expected continue handshake.

Significado: RFC joke code; often used playfully.

Cuándo usar: Easter eggs/test responses.

Causas comunes: Custom humorous API responses.

Ejemplo: Tea endpoint refusing coffee.

Significado: Unofficial rate-limit style response.

Cuándo usar: Custom throttling.

Causas comunes: Client too aggressive.

Ejemplo: Legacy Twitter-style throttling.

Significado: Request sent to wrong server.

Cuándo usar: HTTP/2 connection reuse mismatch.

Causas comunes: TLS/SNI mismatch.

Ejemplo: Shared connection wrong authority.

Significado: Semantically invalid payload.

Cuándo usar: Validation errors.

Causas comunes: Field-level validation fails.

Ejemplo: Email format invalid in signup form.

Significado: Resource is locked.

Cuándo usar: WebDAV locking.

Causas comunes: Concurrent write lock.

Ejemplo: Document locked by another editor.

Significado: Dependent action failed.

Cuándo usar: Batch/transactional operations.

Causas comunes: Previous operation in chain failed.

Ejemplo: Move fails after lock step fails.

Significado: Server unwilling to process replay-risk request.

Cuándo usar: Early data replay protection.

Causas comunes: TLS early data concerns.

Ejemplo: Server asks client to retry safely.

Significado: Switch to newer protocol.

Cuándo usar: Require TLS/new HTTP version.

Causas comunes: Plain HTTP to HTTPS-only service.

Ejemplo: Server requires HTTPS upgrade.

Significado: Conditional request required.

Cuándo usar: Prevent lost updates.

Causas comunes: Missing If-Match/If-Unmodified-Since.

Ejemplo: Update endpoint requires version check.

Significado: Rate limit exceeded.

Cuándo usar: Throttle abusive/high-frequency clients.

Causas comunes: Burst traffic without backoff.

Ejemplo: Client exceeds 100 req/min.

Significado: Headers too large.

Cuándo usar: Cookie/header bloat.

Causas comunes: Oversized cookies.

Ejemplo: Huge cookie payload rejected.

Significado: Blocked by legal demand.

Cuándo usar: Geo/legal restrictions.

Causas comunes: Court/government takedown.

Ejemplo: Content blocked in specific region.

Significado: Generic server failure.

Cuándo usar: Unhandled exceptions.

Causas comunes: App bugs/null pointers.

Ejemplo: Unexpected runtime exception.

Significado: Server lacks requested functionality.

Cuándo usar: Method/feature unsupported.

Causas comunes: Endpoint stub not implemented.

Ejemplo: PATCH not supported by server.

Significado: Invalid upstream response.

Cuándo usar: Proxy/gateway issues.

Causas comunes: Upstream crash/timeouts.

Ejemplo: Nginx receives malformed upstream response.

Significado: Temporary server unavailability.

Cuándo usar: Maintenance/overload.

Causas comunes: Deployment or overload.

Ejemplo: App in maintenance mode.

Significado: Upstream timed out.

Cuándo usar: Proxy timeout waiting upstream.

Causas comunes: Slow database/downstream service.

Ejemplo: API gateway timeout after 30s.

Significado: HTTP version unsupported.

Cuándo usar: Client sends unsupported protocol.

Causas comunes: Old client/proxy mismatch.

Ejemplo: HTTP/0.9 style request rejected.

Significado: Content negotiation config error.

Cuándo usar: Server negotiation loops.

Causas comunes: Misconfigured variants.

Ejemplo: Negotiated variant points to itself.

Significado: Server storage exhausted.

Cuándo usar: WebDAV or storage-backed writes.

Causas comunes: Disk full/quota exceeded.

Ejemplo: Cannot save uploaded file.

Significado: Infinite loop detected.

Cuándo usar: WebDAV depth operations.

Causas comunes: Cyclic bindings.

Ejemplo: Traversal loop breaks operation.

Significado: Further extensions required.

Cuándo usar: Policy extension requirements.

Causas comunes: Missing extension declarations.

Ejemplo: Server expects additional extension info.

Significado: Network login required.

Cuándo usar: Captive portals.

Causas comunes: Public Wi-Fi auth gates.

Ejemplo: User must login to Wi-Fi portal.