This is a list of all the HTTP status codes. A better understanding of these codes will help you understand the under workings of how HTTP works.

Informational

100 – Continue

Indicates that part of a request has been successfully received, and the rest should now be sent.

101 – Switching Protocols

Status code 101 is when the server is changing protocols as defined in the “Upgrade” header that it returns to the browser.

Successful

200 – OK

This just means that the request has been received and understood and is being processed.

201 – Created

This indicates that a request was successful and as a result, a resource has been created.

202 – Accepted

Status code 202 indicates that the server has received and understood the request and has been accepted for processing.

203 – Non-Authoritative Information

This is a lot like a status 200 except the response comes from a third party rather than the original server.

204 – No Content

The request has been received and understood but there is nothing to send back.

205 – Reset Content

An example of this might be if a user fills out a form, and submits it, a status code of 205 means the server is asking the browser to clear the form.

206 – Partial Content

A status code of 206 is a response to a request for part of a document.

Redirection

300 – Multiple Choices

The 300 status code indicates that a resource has moved. The response will include a list of locations that the user agent can select from.

301 – Moved Permanently

A status code of 301 tells a client that the resource they asked for has permanently moved to a new location. It tells the client that it should use the new URL for this resource.

302 – Found

This is when a resource has been temporarily moved to a new location. It tells the client that it should still use the same URL to access the resource.

303 – See Other

This means that the response to the request is found at a different URL. It doesn’t mean the resource has moved, it is just giving the address to where the response can be found.

304 – Not Modified

304 status indicates whether a document is different from the one in the client’s cache.

305 – Use Proxy

A 305 status code tells the client that the requested resource has to be reached through a proxy, which will be specified in the response.

307 – Temporary Redirect

307 is pretty well the same as status 302.

Client Error

400 – Bad Request

A status code of 400 indicates that the server did not understand the request due to bad syntax.

401 – Unauthorized

A 401 status code indicates that the client must be authorized before receiving the resource.

402 – Payment Required

The 402 status code is not in use. It’s listed as “reserved for future use”.

403 – Forbidden

A 403 status code indicates that the client cannot access the requested resource. This could mean that authentication failed, or the user does not have permission.

404 – Not Found

This is probably the most popular. It just means that the page you were looking for cannot be found.

405 – Method Not Allowed

A 405 status code is returned when the client is trying to use a request method (POST, GET) that the server doesn’t allow.

406 – Not Acceptable

The 406 status code means that the server understood and processed the request, but the response is not in the form that the client specified in the header request.

407 – Proxy Authentication Required

The client must be authorized by the proxy before the request can proceed.

408 – Request Timeout

The client didn’t produce a request quick enough. Servers have a set time limit, a 408 indicates that it went past the limit.

409 – Conflict

A 409 status code indicates that the server was unable to complete the request. This might happen if your trying to add, edit, remove a file, and you are unable to.

410 – Gone

A 410 status code is similar to 404, but indicates that the file is permanently gone. Where 404 doesn’t indicate one way or another.

411 – Length Required

The 411 status code occurs when a server refuses to process a request because a content length was not specified.

412 – Precondition Failed

A 412 status code indicates that one of the preconditions of the request was not met.

413 – Request Entity Too Large

The 413 status code indicates that the request was too large. Either by physical limit of the server or a setting on the server.

414 – Request-URI Too Long

The 414 status code simply means that the URL was too long to be processed.

415 – Unsupported Media Type

A 415 status code is returned by a server to indicate that part of the request was in an unsupported format.

416 – Requested Range Not Satisfiable

A 416 status code indicates that the server was unable to fulfill the request. For example, the client requests bytes outside the total bytes of a document.

417 – Expectation Failed

The 417 status code means that one of the headers sent to the server, indicated an expectation the server could not meet.

Server Error

500 – Internal Server Error

A 500 status code means the server came across something unexpected and could not complete the request.

501 – Not Implemented

The server does not support all that is needed for the request to be completed.

502 – Bad Gateway

If the server is acting as a proxy, received a response from a server further up that judged the request as invalid.

503 – Service Unavailable

When a server can’t complete a request because it is too busy (overloaded)

504 – Gateway Timeout

When a server is acting as a proxy, and a server upstream is taking too long.

505 – HTTP Version Not Supported

A 505 status code is returned when the HTTP version indicated in the request is no supported. The response should indicate which HTTP versions are supported.