HTTP Status Codes

Quick reference for all HTTP response status codes. Search by code number or keyword, see causes and how to fix common errors.

37 status codes

100

ContinueServer received request headers. Client should proceed with body.

1xx▼

101

Switching ProtocolsServer is switching to protocol requested by client.

1xx▼

103

Early HintsServer sends preliminary headers before final response.

1xx▼

200

OKRequest succeeded. Response body contains the result.

2xx▼

201

CreatedRequest succeeded and a new resource was created.

2xx▼

202

AcceptedRequest accepted for processing, but not yet completed.

2xx▼

204

No ContentRequest succeeded but there is no content to return.

2xx▼

206

Partial ContentServer is returning only part of the resource.

2xx▼

301

Moved PermanentlyResource has permanently moved to a new URL.

3xx▼

302

FoundResource temporarily moved to a different URL.

3xx▼

303

See OtherRedirect to a different resource using GET.

3xx▼

304

Not ModifiedResource has not changed since last request.

3xx▼

307

Temporary RedirectTemporary redirect preserving the HTTP method.

3xx▼

308

Permanent RedirectPermanent redirect preserving the HTTP method.

3xx▼

400

Bad RequestServer cannot process the request due to client error.

4xx▼

401

UnauthorizedAuthentication is required but was not provided or is invalid.

4xx▼

403

ForbiddenServer understood the request but refuses to authorize it.

4xx▼

404

Not FoundRequested resource does not exist on the server.

4xx▼

405

Method Not AllowedHTTP method is not supported for this endpoint.

4xx▼

406

Not AcceptableServer cannot produce response matching Accept headers.

4xx▼

408

Request TimeoutServer timed out waiting for the client request.

4xx▼

409

ConflictRequest conflicts with the current state of the resource.

4xx▼

410

GoneResource has been permanently deleted and will not return.

4xx▼

413

Payload Too LargeRequest body exceeds the server size limit.

4xx▼

415

Unsupported Media TypeServer does not support the request body format.

4xx▼

422

Unprocessable EntityRequest is well-formed but contains semantic errors.

4xx▼

429

Too Many RequestsClient has sent too many requests in a given time.

4xx▼

431

Request Header Fields Too LargeServer refuses request because headers are too large.

4xx▼

451

Unavailable For Legal ReasonsResource is blocked due to legal demands.

4xx▼

500

Internal Server ErrorServer encountered an unexpected error.

5xx▼

501

Not ImplementedServer does not support the functionality required.

5xx▼

502

Bad GatewayServer acting as proxy received an invalid response from upstream.

5xx▼

503

Service UnavailableServer is temporarily unable to handle requests.

5xx▼

504

Gateway TimeoutProxy/gateway did not receive a timely response from upstream.

5xx▼

507

Insufficient StorageServer cannot store the representation needed to complete the request.

5xx▼

508

Loop DetectedServer detected an infinite loop while processing the request.

5xx▼

511

Network Authentication RequiredClient needs to authenticate to gain network access.

5xx▼

HTTP Status Code Reference — Complete Guide

HTTP status codes are three-digit numbers returned by a web server in response to every request. They tell the client whether the request succeeded, was redirected, or failed — and why. This reference covers all standard codes with practical explanations, real-world causes, and actionable fixes.

HTTP Status Code Categories

1xx Informational — server received the request, continuing to process. Rarely seen except 101 (WebSocket upgrade). 2xx Success — request was accepted. 200 OK is the most common. 201 Created is returned after successful POST. 204 No Content for successful DELETE with no response body.

3xx Redirection — client needs additional action. 301 Moved Permanently passes SEO authority. 302 Found is temporary redirect. 304 Not Modified tells the browser to use cache. 4xx Client Errors — request has a problem. 400 Bad Request = malformed syntax. 401 Unauthorized = missing auth. 403 Forbidden = authenticated but not authorized. 404 Not Found is the most well-known error.

5xx Server Errors — server failed to fulfill a valid request. 500 Internal Server Error is a catch-all. 502 Bad Gateway = upstream returned invalid response (common with nginx). 503 Service Unavailable = overloaded or maintenance. 504 Gateway Timeout = upstream didn't respond in time.

Most Common HTTP Errors and How to Fix Them

404 Not Found — check URL for typos, verify resource exists, check rewrite rules, confirm the route is defined. 500 Internal Server Error — check application logs (not web server logs), look for unhandled exceptions, database failures, or missing env variables. 502 Bad Gateway — verify upstream app is running, check port matches proxy config, review memory limits (common: app OOM-killed).

429 Too Many Requests — you're hitting a rate limit. Implement exponential backoff and respect Retry-After headers. 401 vs 403 — 401 means "who are you?" (authentication needed), 403 means "I know who you are, but access denied" (authorization).

HTTP Status Codes for REST APIs

Best practices: return 201 for resource creation with a Location header, 204 for successful deletions, 400 for validation errors with details in the body, 409 Conflict for duplicates, and 422 Unprocessable Entity for semantically wrong requests. Include machine-readable error codes alongside HTTP status for easier client handling.