HTTP Status Codes — Complete Reference Guide

Informational

100

Continue

The server has received the request headers and the client should proceed to send the request body.

101

Switching Protocols

The server is switching protocols as requested by the client (e.g., upgrading to WebSocket).

102

Processing

The server has received and is processing the request, but no response is available yet (WebDAV).

103

Early Hints

Used to return some response headers before the final HTTP message, allowing preloading of resources.

Success

200

The request has succeeded. The meaning depends on the HTTP method used.

201

Created

The request has been fulfilled and a new resource has been created.

202

Accepted

The request has been accepted for processing, but the processing has not been completed.

203

Non-Authoritative Information

The returned metadata is from a local or third-party copy, not the origin server.

204

No Content

The server has fulfilled the request but does not need to return a response body.

205

Reset Content

The server has fulfilled the request and asks the client to reset the document view.

206

Partial Content

The server is delivering only part of the resource due to a Range header sent by the client.

207

Multi-Status

A multi-status response conveying information about multiple resources (WebDAV).

208

Already Reported

Members of a DAV binding have already been enumerated and are not included again (WebDAV).

Redirection

301

Moved Permanently

The requested resource has been permanently moved to a new URL. Future requests should use the new URL.

302

Found

The resource resides temporarily under a different URL. The client should continue to use the original URL.

303

See Other

The response can be found at a different URI and should be retrieved using a GET method.

304

Not Modified

The resource has not been modified since the version specified by the request headers (caching).

307

Temporary Redirect

The request should be repeated with another URI, but the HTTP method must not change.

308

Permanent Redirect

The resource has permanently moved and the HTTP method must not change in the redirect.

Client Error

400

Bad Request

The server cannot process the request due to malformed syntax or invalid parameters.

401

Unauthorized

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

403

Forbidden

The server understood the request but refuses to authorize it.

404

Not Found

The server cannot find the requested resource. The URL may be incorrect or the resource deleted.

405

Method Not Allowed

The HTTP method used is not supported for the requested resource.

406

Not Acceptable

The server cannot produce a response matching the list of acceptable values in the request headers.

407

Proxy Authentication Required

The client must first authenticate itself with the proxy.

408

Request Timeout

The server timed out waiting for the request.

409

Conflict

The request conflicts with the current state of the target resource.

410

Gone

The resource is permanently no longer available and no forwarding address is known.

411

Length Required

The server requires a Content-Length header in the request.

412

Precondition Failed

One or more conditions in the request header fields evaluated to false.

413

Payload Too Large

The request entity exceeds limits defined by the server.

414

URI Too Long

The URI provided was too long for the server to process.

415

Unsupported Media Type

The media format of the requested data is not supported by the server.

416

Range Not Satisfiable

The range specified by the Range header cannot be fulfilled.

418

I'm a Teapot

The server refuses to brew coffee because it is a teapot (RFC 2324).

422

Unprocessable Entity

The request was well-formed but semantically erroneous (WebDAV).

425

Too Early

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

429

Too Many Requests

The user has sent too many requests in a given amount of time (rate limiting).

431

Request Header Fields Too Large

The server refuses the request because header fields are too large.

451

Unavailable For Legal Reasons

The resource is unavailable due to legal demands (censorship, court order).

Server Error

500

Internal Server Error

The server encountered an unexpected condition that prevented it from fulfilling the request.

501

Not Implemented

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

502

Bad Gateway

The server acting as a gateway received an invalid response from the upstream server.

503

Service Unavailable

The server is temporarily unable to handle the request (overloaded or under maintenance).

504

Gateway Timeout

The server acting as a gateway did not receive a timely response from the upstream server.

505

HTTP Version Not Supported

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

507

Insufficient Storage

The server cannot store the representation needed to complete the request (WebDAV).

508

Loop Detected

The server detected an infinite loop while processing the request (WebDAV).

511

Network Authentication Required

The client needs to authenticate to gain network access (captive portal).

What Are HTTP Status Codes?

HTTP status codes are three-digit numbers returned by a web server in response to a client's request. They indicate whether the request was successful, redirected, resulted in an error, or requires further action. Understanding these codes is essential for debugging APIs, web applications, and monitoring infrastructure.

Status Code Categories

1xx Informational: The request was received and processing continues
2xx Success: The request was successfully received, understood, and accepted
3xx Redirection: Further action needs to be taken to complete the request
4xx Client Error: The request contains bad syntax or cannot be fulfilled
5xx Server Error: The server failed to fulfill a valid request

Monitoring HTTP Status Codes

Tracking HTTP status codes is critical for uptime monitoring. A spike in 5xx errors indicates server-side issues, while 4xx errors may signal broken links or misconfigured APIs. Automated monitoring tools can alert you the moment unexpected status codes appear.

HTTP Status Code Reference

Search Status Codes