Ultimate Guide to HTTP Status Codes

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What are HTTP Status Codes?

Find our comprehensive guide to the HTTP status codes (Hypertext Transfer Protocol). These status codes are issued by a server in response to a client’s request made to the server and inform the end user of what action has or has not been performed.

 

All HTTP response status codes are separated into five classes (or categories). The first digit of the status code defines the class of response. The last two digits do not have any class or categorization role. There are five values for the first digit:

  • 1xx (Informational): The request was received, continuing process
  • 2xx (Successful): The request was successfully received, understood, and accepted
  • 3xx (Redirection): Further action needs to be taken in order to complete the request
  • 4xx (Client Error): The request contains bad syntax or cannot be fulfilled
  • 5xx (Server Error): The server failed to fulfil an apparently valid request

 

Ultimate Guide to HTTP Status Codes

Status Codes:

1xx Informational

*** In Plain English: Hold on while we continue with the process. ***

100 Continue

This interim response indicates that everything so far is OK and that the client should continue with the request or ignore it if it is already finished.

101 Switching Protocol

This code is sent in response to an Upgrade request header by the client and indicates the protocol the server is switching to.

102 Processing WebDAV

This code indicates that the server has received and is processing the request, but no response is available yet.

103 Checkpoint Draft Post Put

Indicates to the client that the server is likely to send a final response with the header fields included in the informational response. Resumes aborted PUT or POST requests in Resumable HTTP Requests Proposal.

122 Request URI Too Long IE7

An IE7-only code that indicates that the URI is longer than the maximum 2,083 characters.

 

2xx Successful

*** In Plain English: Here you go with the completed actions. ***

200 OK

The request has succeeded. The meaning of a success varies depending on the HTTP method:

GET: The resource has been fetched and is transmitted in the message body.

HEAD: The entity headers are in the message body.

PUT or POST: The resource describing the result of the action is transmitted in the message body.

TRACE: The message body contains the request message as received by the server

201 Created

The request has succeeded and a new resource has been created as a result of it. This is typically the response sent after a POST request, or after some PUT requests.

202 Accepted

The request has been received but not yet acted upon. It is non-committal, meaning that there is no way in HTTP to later send an asynchronous response indicating the outcome of processing the request. It is intended for cases where another process or server handles the request, or for batch processing.

203 Non-Authoritative Information 1.1

This response code means returned meta-information set is not exactly set as available from the origin server but collected from a local or a third-party copy. Except for this condition, 200 OK response should be preferred instead of this response.

204 No Content

There is no content to send for this request, but the headers may be useful. The user-agent may update its cached headers for this resource with the new ones.

205 Reset Content

This response code is sent after accomplishing request to tell user agent to reset document view which sent this request.

206 Partial Content

This response code is used because of range header sent by the client to separate download into multiple streams.

207 Multi-Status WebDAV 4918

A Multi-Status response conveys information about multiple resources in situations where multiple status codes might be appropriate.

208 Multi-Status WebDAV 5842

Used inside a DAV: propstat response element to avoid enumerating the internal members of multiple bindings to the same collection repeatedly.

226 IM Used HTTP Delta encoding 3229 Get

The server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations applied to the current instance.

 

3xx Redirection

*** In Plain English: Go away until its fixed. ***

300 Multiple Choice

The request has more than one possible response. The user-agent or user should choose one of them. There is no standardized way of choosing one of the responses.

301 Moved Permanently

This response code means that the URI of the requested resource has been changed. Probably, the new URI would be given in the response.

302 Found

This response code means that the URI of the requested resource has been changed temporarily. New changes in the URI might be made in the future. Therefore, this same URI should be used by the client in future requests.

303 See Other 1.1

The server sent this response to direct the client to get the requested resource at another URI with a GET request.

304 Not Modified

This is used for caching purposes. It tells the client that the response has not been modified, so the client can continue to use the same cached version of the response.

305 Use Proxy 1.1

Was defined in a previous version of the HTTP specification to indicate that a requested response must be accessed by a proxy. It has been deprecated due to security concerns regarding the in-band configuration of a proxy.

306 Switch Proxy Unused

This response code is no longer used, it is just reserved currently. It was used in a previous version of the HTTP 1.1 specification.

307 Temporary Redirect 1.1

The server sends this response to direct the client to get the requested resource at another URI with the same method that was used in the prior request. This has the same semantics as the 302 Found HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.

308 Permanent Redirect Draft Put Post

This means that the resource is now permanently located at another URI, specified by the Location: HTTP Response header. This has the same semantics as the 301 Moved Permanently HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.

 

4xx Client Error

*** In Plain English: You made a mistake, please rectify. ***

400 Bad Request

This response means that server could not understand the request due to invalid syntax.

401 Unauthorized

Although the HTTP standard specifies “unauthorized”, semantically this response means “unauthenticated”. That is, the client must authenticate itself to get the requested response.

402 Payment Required Res

This response code is reserved for future use. Initial aim for creating this code was using it for digital payment systems however this is not used currently.

403 Forbidden

The client does not have access rights to the content, i.e. they are unauthorized, so the server is rejecting to give the proper response. Unlike 401, the client’s identity is known to the server.

404 Not Found

The server cannot find the requested resource. In the browser, this means the URL is not recognized. In an API, this can also mean that the endpoint is valid but the resource itself does not exist. Servers may also send this response instead of 403 to hide the existence of a resource from an unauthorized client. This response code is probably the most famous one due to its frequent occurrence on the web.

405 Method Not Allowed

The request method is known by the server but has been disabled and cannot be used. For example, an API may forbid DELETE-ing a resource. The two mandatory methods, GET and HEAD, must never be disabled and should not return this error code.

406 Not Acceptable

This response is sent when the web server, after performing server-driven content negotiation, doesn’t find any content following the criteria are given by the user agent.

407 Proxy Authentication Required

This is similar to 401 but authentication is needed to be done by a proxy.

408 Request Timeout

This response is sent on an idle connection by some servers, even without any previous request by the client. It means that the server would like to shut down this unused connection. This response is used much more in some browsers, like Chrome, Firefox 27+, or IE9, use HTTP pre-connection mechanisms to speed up surfing. Also, note that some servers merely shut down the connection without sending this message.

409 Conflict

This response is sent when a request conflicts with the current state of the server.

410 Gone

This response would be sent when the requested content has been permanently deleted from the server, with no forwarding address. Clients are expected to remove their caches and links to the resource. The HTTP specification intends this status code to be used for “limited-time, promotional services”. APIs should not feel compelled to indicate resources that have been deleted with this status code.

411 Length Required

Server rejected the request because the Content-Length header field is not defined and the server requires it.

412 Precondition Failed

The client has indicated preconditions in its headers which the server does not meet.

413 Payload Too Large

Request entity is larger than limits defined by the server; the server might close the connection or return a Retry-After header field.

414 URI Too Long

The URI requested by the client is longer than the server is willing to interpret.

415 Unsupported Media Type

The media format of the requested data is not supported by the server, so the server is rejecting the request.

416 Requested Range Not Satisfiable

The range specified by the Range header field in the request can’t be fulfilled; it’s possible that the range is outside the size of the target URI’s data.

417 Expectation Failed

This response code means the expectation indicated by the Expect request-header field can’t be met by the server.

418 I’m a teapot 2324

The server refuses the attempt to brew coffee with a teapot. Created in 1998 as an April Fool’s joke.

421 Misdirected Request WebDav 4918

The request was directed at a server that is not able to produce a response. This can be sent by a server that is not configured to produce responses for the combination of scheme and authority that are included in the request URI.

422 Unprocessable Entity WebDAV 4918

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

423 Locked WebDAV 4918

The resource that is being accessed is locked.

424 Failed Dependency WebDAV 4918

The request failed due to the failure of a previous request.

425 Unordered Collection 3648

The attempt to set the position of an internal collection member in an unordered collection or in a collection with a server-maintained ordering failed.

426 Upgrade Required 2817

The server refuses to perform the request using the current protocol but might be willing to do so after the client upgrades to a different protocol. The server sends an Upgrade header in a 426 response to indicate the required protocol(s).

428 Precondition Required Draft

The origin server requires the request to be conditional. Intended to prevent the ‘lost update’ problem, where a client GETs a resource’s state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict.

429 Too Many Requests Draft

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

431 Request Header Fields Too Large Draft

The server is unwilling to process the request because its header fields are too large. The request MAY be resubmitted after reducing the size of the request header fields.

444 No Response Nginx

In Nginx logs as a malware deterrent, indicates that the server returned no information and closed the connection.

449 Retry With MS

Microsoft extension indicating that the request should be retried after performing a specific action.

450 Blocked By Windows Parental Controls MS

Microsoft extension indicating that Windows Parental Controls are turned on and blocking access to the page in question.

451 Unavailable For Legal Reasons Draft

The user requests an illegal resource, such as a web page censored by a government. Indicates that resource access has been denied for legal reasons such as censorship or government-mandated blocked access. Defined in the Internet draft as “A New HTTP Status Code for Legally-restricted Resources.”

494 Request Header Too Large Nginx

Similar to 431, Nginx internal code earlier in version 0.9.4

495 Cert Error Nginx

Nginx internal code indicating that SSL client certificate error has occurred.

496 No Cert Nginx

Nginx internal code indicating that the client didn’t provide a certificate.

497 HTTP to HTTPs Nginx

Nginx internal code indicating that plain HTTP requests were sent to HTTPS port.

498 Token Expired /Invalid

Returned by ArcGIS for Server when the token is expired or otherwise invalid.

499 Client Closed Request Nginx

In Nginx logs, indicates that the connection has been closed by the client while the server is still processing its request, in which case the server is unable to send a status code back.

 

5xxServer Error

*** In Plain English: Server performed an error. ***

500 Internal Server Error

The server has encountered a situation it doesn’t know how to handle.

501 Not Implemented

The request method is not supported by the server and cannot be handled. The only methods that servers are required to support (and therefore that must not return this code) are GET and HEAD.

502 Bad Gateway

This error response means that the server while working as a gateway to get a response needed to handle the request, got an invalid response.

503 Service Unavailable

The server is not ready to handle the request. Common causes are a server that is down for maintenance or that is overloaded. Note that together with this response, a user-friendly page explaining the problem should be sent. This response should be used for temporary conditions and the Retry-After: HTTP header should, if possible, contain the estimated time before the recovery of the service. The webmaster must also take care of the caching-related headers that are sent along with this response, as these temporary condition responses should usually not be cached.

504 Gateway Timeout

This error response is given when the server is acting as a gateway and cannot get a response in time.

505 HTTP Version Not Supported

The HTTP version used in the request is not supported by the server.

506 Variant Also Negotiates 2295

The server has an internal configuration error: transparent content negotiation for the request results in a circular reference.

507 Insufficient Storage WebDav 4918

The server has an internal configuration error: 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 WebDAV 5842

The server detected an infinite loop while processing the request.

509 Bandwith Limit Exceeded Nostd

Use unknown. Status code not specified by any RFCs.

510 Not Extended 2774

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

511 Network Authentication Required Draft

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

598 Network Read Timeout Error Nostd

Used by Microsoft HTTP proxies to signal a network read timeout behind the proxy to a client in front of the proxy.

599 Network Connect Timeout Error Nostd

Used by Microsoft HTTP proxies to signal a network read timeout behind the proxy to a client in front of the proxy.

 

HTTP Code Comments

WebDav  –  WebDav Extension

1.1  –  HTTP/1.1

GET, POST, PUT, POST  –  For these methods only

IE  –  IE Extension

MS  –  MS Extension

Nginx  –  Nginx Extension

2518, 2817, 2295, 2774, 3229, 4918, 5842  –  RFC number

Draft  –  Proposed Draft

Nostd  –  Non standard Extension

Res  –  Reserved for future use

Unused  –  No more in use, Deprecated

 

Our HTTP Status Codes

We hope that you have found this guide to the HTTP Status Codes useful and share, like or tag for future reference. If you wish us to include an additional term or phrase and elaborate on it with an example, please add your comments in the comment area below. Many thanks and we hope we have helped you on your way to becoming an SEO expert.

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