Understanding the Meanings Behind Common HTTP Response Codes

Sometimes you may see that your computer screen shows the HTTP error codes and addresses - "The requested URL /does_not_exist was not found on this server". Sometimes you get this type of error code, sometimes didn't. So, what is HTTP response status codes and what do mean these codes? Here, in this article, we will explain HTTP response status codes and their meaning.

What is HTTP status code?

HTTP stands for Hypertext Transfer Protocol. It's a method to communicate between you and servers. When you click a link and types in a URL or submit a form, their browser sends a request to a server for information. It might be asking for a page, or sending data, that is called an HTTP Request. When a server receives that request, it sends back an HTTP Response, with information. One of the most common Response codes is 404. There are few more status codes sent by servers. These status codes indicate a provisional response.

The codes are grouped in five classes - informational responses, successful responses, redirects, client errors, and servers errors.

1. Informational responses

100 - Continue

100 indicates it's a part of a request that has been received without any problems and that the rest of the request should now be sent.

101 - Switching Protocols

101 means that the requester has asked the server to switch protocols; and the server has agreed to do.

102 - Processing

102 indicates that the server has received and processing that request, but not getting any response yet. It prevents the client through time out and assumed that lost the request.

103 - Early Hints

103 indicates that it used to return some response headers before final HTTP message.

2. Successful responses

200

200 means that the request was received and understood and it is being processed.

201 - Created

201 code indicates that a request was successful. As a result, a resource has been created.

202 - Accepted

202 indicates that server has received and it has been accepted for processing. It may not be processed immediately.

203 - Non-Authoritative Information

203 means that the request was received and information sent back from a third party.

204 - No Content

204 code means that the request was received, but there is no need to send any data back.

205 - Reset Content

205 code is a type of request from the server to reset the document.

206 - Partial Content

206 is a response to a request for part of a document. It used by advanced caching tools when a user agent requests only a small part of the page.

207 - Multi-Status

It indicates the information about multiple resources in situations where multiple status codes might be appropriate.

208 - Multi-Status

It responses the element to avoid enumerating the internal members of multiple bindings to the same collection repeatedly.

226 - IM Used

This the response is a representation of the result of one or more instance-manipulations applied to the current instance.

3. Redirection messages

300 - Multiple Choices

300 indicates that a resource has moved. It will also include a list of locations from which the user agent can able to select the most appropriate.

301 - Moved Permanently

301 indicates that the resource has permanently moved to a new location. The response should also include this location. The client to use the new URL

302 - Found

302 indicates that the resource has temporarily moved to a new location. The response should also include this location. The client should carry on using the same URL to access this resource.

303 - See Other

303 code indicates that the response to the request can be found at the specified URL and retrieve. It specify the address to which the response to the request can be found.

304 - Not Modified

304 is sent in response to a request that asked for the document only if it was newer than the one.

305 - Use Proxy

305 code tells the client that the requested resource has to be reached through a proxy.

306 - Switch Proxy

It originally means subsequent requests should use the specified proxy. But no longer it used.

307 - Temporary Redirect

307 code is sent when a document is temporarily available at a different URL.

308 - Permanent Redirect

It means the request and all future requests should be repeated using another URI. 307 and 308 parallel the behaviors of 302 and 301 but do not allow the HTTP method to change.

4. Client error responses

400 - Bad Request

400 indicates that the server did not understand the request because of bad syntax.

401 - Unauthorized

401 code indicates that the client must be authorized by the server before a resource can be accessed.

402 - Payment Required

402 code indicates as "reserved for future use". But it is not currently in use.

403 - Forbidden

403 indicates that the client cannot access the requested resource. It means the wrong username and password were  sent in the request or the permissions on the server do not allow for that.

404 - Not Found

404 indicates that the requested resource was not found at the URL given.

405

405 code is returned when the client has tried to use a request method that the server does not allow.

406 - Not Acceptable

406 means that the response is of a form that the client cannot understand. A client sends, as part of a request, headers indicating what types of data it can use. 406 error is returned when the response is of a type.

407 - Proxy Authentication Required

407 code means that the client must be authorized by the proxy before the request can proceed.

408 - Request Timeout

408 means that the client did not produce a request quickly enough.

409 - Conflict

409 indicates that the server was unable to complete the request because a file would need to be edited, created or deleted.

410

410 code indicates that a resource has permanently gone.

411 - Length Required

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

412 - Precondition Failed

412 indicates that one of the conditions the request was made under has failed.

413 - Request Too Large

413 indicates that the request was larger than the server is able to handle, either due to physical constraints or to settings.

414 - URI Too Long

414 code indicates the URL requested by the client was longer than it can process.

415

415 code indicates that part of the request was in an unsupported format.

416 - Not Satisfiable

416 indicates that the server was unable to fulfill the request.

417 - Expectation Failed

417 means that the server was unable to properly complete the request.

418

The server refuses the attempt to brew coffee with a teapot.

421

This indicates the request was directed at a server that is not able to produce a response.

422 - Unprocessable Entity

This indicates the request was well-formed but was unable to be followed due to semantic errors.

423

This indicates the resource is being accessed is locked.

424

This indicates the request failed because it depended on another request and that request failed.

426 - Upgrade

This indicates the client should switch to a different protocol such as TLS/1.0, and given in the Upgrade header field.

428 - Precondition

This indicates the origin server requires the request to be conditional.

429 - Many Requests

This indicates the user has sent too many requests in given amount of time.

431 - Request Header Fields Too Large

This indicates the server is unwilling to process the request because either an individual header field or all the header fields collectively are too large.

451 - Unavailable

This indicates a server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.

5. Server error responses

500 - Internal Server Error

500 code indicates that the server encountered something it didn't expect and was unable to complete the request.

501 - Not Implemented

501 code indicates that the server does not support all that is needed for the request to be completed.

502 - Bad Gateway

502 indicates that a server while acting as a proxy, received a response from a server further upstream that it judged invalid.

503 - Service Unavailable

503 code is most often seen on extremely busy servers. It indicates that the server was unable to complete the request due to a server overload.

504 - Gateway Timeout

504 code is returned when a server acting as a proxy has waited too long for a response from a server further upstream.

505 - HTTP Not Supported

505 code is returned when the HTTP version indicated in the request is not supported.

506

This indicates the server has an internal configuration error. Transparent content negotiation for the request results in a circular reference.

507 - Insufficient Storage

This indicates the chosen variant resource is configured to engage in transparent content negotiation itself and is therefore not a proper end point in the negotiation process.

508 - Loop Detected

This indicates the server detected an infinite loop while processing the request.

510 - Not Extended

This indicates further extensions to the request are required for the server to fulfill it.

511 - Network Authentication

511 code indicates that the client needs to authenticate to gain network access.