How to troubleshoot common HTTP errors

Common http errors and their fixes

1xx: Informational

This group of status codes indicates a provisional response, consisting only of the Status Line and optional headers, and is terminated by an empty line.
100 - Continue

The client should continue with its request by sending the remainder of the request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server.

101 - Switching Protocols

The client request has asked the server to switch protocols and the server is acknowledging that it will do so and comply with the client's request.

2xx: Success

This group of status codes indicates that the client's request was successfully received, understood, and accepted
200 - OK

This server response means that the request is successful and the requested information is returned to the client.

201 - Created

The request has been fulfilled, resulting in the creation of a new resource

3xx - Redirection

This group of status codes indicates that further action needs to be taken by the user agent in order to complete the request.
300 - Multiple Choices

Indicates multiple options for the resource from which the client may choose. For example, this code could be used to present multiple video format options, to list files with different filename extensions.

302 - Found (Moved Temporarily)

The server responds with a 302 error message when the requested resource has been temporarily moved to a different URL. Usually the server response contains a reference to the new URL where the resource was moved. Clients should continue to use the request URL since the redirection might be altered on occasion.

304 - Not Modified

Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match. In such case, there is no need to retransmit the resource since the client still has a previously-downloaded copy

306 - Switch Proxy (Unused)

The 306 status code was used in a previous version of the specification, but is no longer used and currently the code is reserved.

308 - Permanent Redirect

With this response a web server informs the client that all future requests should be sent using a different URI.

301 - Moved Permanently

The server responds with a 301 error message when the requested resource has been assigned a new permanent URL.

303 - See Other

The response to the request can be found under another URI using the GET method. When received in response to a POST (or PUT/DELETE), the client should presume that the server has received the data and should issue a new GET request to the given URI

305 - Use Proxy

The requested resource is available only through a proxy, the address for which is provided in the response.

307 - Temporary Redirect

With this response a web server informs the client that the requested URL resides temporarily under a different URL. The new temporary URL should be given in the response from the server. The recipient is expected to follow the redirection but future requests can still be directed to the original URL.

4xx - Client Error

This group of HTTP status codes indicates that the request for the resource contains bad syntax or cannot be filled for some other reason, presumably by fault of the client sending the request. Except when responding to a HEAD request, the server SHOULD include an explanation of the error situation and whether it is a temporary or permanent condition.

400 - Bad Request

The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, size too large, invalid request message framing, or deceptive request routing).

402 - Payment Required

This code is reserved for future use. It was intended the 402 code to be used as part of some form of digital payment, but that has not happened.

404 - File Not Found

The requested resource could not be found but may be available in the future. Subsequent requests by the client are permissible.

406 - Not Acceptable

The requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request.

408 - Request Timeout

The server timed out waiting for the request. According to HTTP specifications: "The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.

410 - Gone

The web server responds with this error when the requested resource is no longer available at the server, will not be available again and no forwarding address is known. This error is similar to 404, but 410 is permanent.

412 - Precondition Failed

The server does not meet one of the preconditions that the requester put on the request.

414 - Request-URL Too Long

The URI provided was too long for the server to process. Often the result of too much data being encoded as a query-string of a GET request, in which case it should be converted to a POST request. Called "Request-URI Too Long" previously.

416 - Requested Range Not Satisfiable

The client has asked for a portion of the file (byte serving), but the server cannot supply that portion. For example, if the client asked for a part of the file that lies beyond the end of the file.Called "Requested Range Not Satisfiable" previously.

422 - Unprocessable entity

he request was well-formed but was unable to be followed due to semantic errors.

424 - Failed dependency

The request failed because it depended on another request and that request failed

401 - Unauthorized

This error message means User authentication is required by the responding server or that authorization has been refused for the provided credentials with the request.

403 - Forbidden

The request sent to the server was a legal request, the server understood it but is refusing to respond to it and to process it. Authorization will not help in this case.

405 - Method Not Allowed

A request method is not supported for the requested resource; for example, a GET request on a form that requires data to be presented via POST, or a PUT request on a read-only resource.

407 - Proxy Authentication Required

This error code is similar to 401 (Unauthorized) and the server responds with 407 error when the request from the client (web browser or our monitoring agent) was correct, but access to the URL resource requires that the client must first authenticate itself with the proxy.

409 - Conflict

Indicates that the request could not be processed because of conflict in the request, such as an edit conflict between multiple simultaneous updates.

411 - Length Required

This error code means that the server refuses to accept the request without a defined content-length. The client should repeat the request adding a valid content-length header field containing the length of the message body in the request message.

413 - Request Entity Too Large

The server is refusing to process a request because the request entity is larger than the server is willing or able to process. The server may close the connection to prevent the client from continuing the request.

415 - Unsupported Media Type

The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.

417 - Expectation Failed

The web server responds with this status code when the expectation given in an Expect request-header field could not be fulfilled by this server, or, if the server is a proxy and has clear evidence that the request could not be fulfilled by the next-hop server.

423 - Locked

The resource that is being accessed is locked.

5xx - Server Error

This group of HTTP status codes indicates that the server is aware that it is on error or is incapable of performing the request. The server response usually includes an explanation of the error situation and if it is a temporary or permanent condition. These response codes in this group are applicable to any request method.

500 - Internal Server Error

A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.

502 - Bad Gateway

The server was acting as a gateway or proxy and received an invalid response from the upstream server.

504 - Gateway Timeout

The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.

506 Variant Also Negotiates

Transparent content negotiation for the request results in a circular reference.

508 Loop Detected

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

501 - Not Implemented

The server either does not recognize the request method, or it lacks the ability to fulfil the request. Usually this implies future availability (e.g., a new feature of a web-service API).

503 - Service Unavailable

The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.

505 - HTTP Version Not Supported

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

507 Insufficient Storage

The server is unable to store the representation needed to complete the request.

510 Not Extended

Further extensions to the request are required for the server to fulfil it.

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