March 16, 2016

Learn What the HTTP Status and Error Codes Means

HTTP Status and Error Codes

HTTP Status and Error Codes, with their Definitions

Sometimes when we try to access a particular website, it won't open and gives an HTTP error message. We try again and again, but we fails every times and the website shows the HTTP error message.
Occasionally, many of us face this kind of problem. And if we have no idea about the problem, it's very difficult to solve.

How many of us know that what the HTTP Error or Status codes means?

How and when we can access the website which is giving error?

If you do not know, then this list of HTTP error / Status codes may be helpful to you.
From this list you can find out what the code means. And if you know what error code means, half of your problem is resolved.

These codes are divided into 5 classes, which are as follows:

1xx Informational Error Codes:

Status codes that indicate a provisional response and require the client to take action to continue.

100 Continue
The client should continue with its request.

101 Switching Protocols
The client has asked the server to switch protocols and the server is acknowledging that it will do so.

102 Processing (WebDAV; RFC 2518)
This code indicates that the server has received and is processing the request, but no response is available yet. This prevents the client from timing out and assuming the request was lost.

2xx Success Status Codes:

This class of status codes indicates the action requested by the client was received, understood, accepted and processed successfully.

200 OK
The server has received and successfully processed the request.

201 Created
The request has been fulfilled and resulted in a new resource being created.

202 Accepted
The server has accepted the request, but hasn't yet processed it.

203 Non-Authoritative Information (since HTTP/1.1)
The server successfully processed the request, but is returning information that may be from another source.

204 No Content
The server successfully processed the request, but is not returning any content. Usually used as a response to a successful delete request.

205 Reset Content
The server successfully processed the request, but is not returning any content. Unlike a 204 response, this response requires that the client reset the document view.

206 Partial Content (RFC 7233)
The server is delivering only part of the resource (byte serving) due to a range header sent by the client.

207 Multi-Status (WebDAV; RFC 4918)
The message body that follows is an XML message and can contain a number of separate response codes, depending on how many sub-requests were made.

208 Already Reported (WebDAV; RFC 5842)
The members of a DAV binding have already been enumerated in a previous reply to this request, and are not being included again.

226 IM Used (RFC 3229)
The server has fulfilled a 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 Codes:

This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection.

300 Multiple Choices
Indicates multiple options for the resource that the client may follow. It, for instance, could be used to present different format options for video, list files with different extensions.

301 Moved Permanently
This and all future requests should be directed to the given URI.

302 Found
This is a temporary response to request found via alternative URI.

303 See Other (since HTTP/1.1)
The response to the request can be found under another URI using a GET method.

304 Not Modified (RFC 7232)
Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match. This means that there is no need to re-transmit the resource, since the client still has a previously-downloaded copy.

305 Use Proxy (since HTTP/1.1)
The requested resource is only available through a proxy, whose address is provided in the response. Many HTTP clients (such as Mozilla and Internet Explorer) do not correctly handle responses with this status code, primarily for security reasons.

306 Switch Proxy
No longer used, and the code is reserved. Originally meant "Subsequent requests should use the specified proxy.

307 Temporary Redirect (since HTTP/1.1)
In this case, The server is currently responding to the request with a page from a different location, but the client should continue to use the original location for future requests.

308 Permanent Redirect (RFC 7538)
The request, and all future requests should be repeated using another URI. 307 and 308 (as proposed) parallel the behaviors of 302 and 301, but do not allow the HTTP method to change. So, for example, submitting a form to a permanently redirected resource may continue smoothly.

4xx Client Error Codes:

These status codes indicate that there was likely an error in the request which prevented the server from being able to process it.

400 Bad Request
The server cannot or will not process the request due to something that is perceived to be a client error (e.g., malformed request syntax, invalid request message framing, or deceptive request routing).

401 Unauthorized (RFC 7235)
Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided. The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource.

402 Payment Required
Reserved for future use. The original intention was that this code might be used as part of some form of digital cash or micro-payment scheme, but that has not happened, and this code is not usually used. YouTube uses this status if a particular IP address has made excessive requests, and requires the person to enter a CAPTCHA. Some work has been done to implement payments via the digital currency Bitcoin automatically on a 402 request.

403 Forbidden
The request was a valid request, but the server is refusing to respond to it. Unlike a 401 Unauthorized response, authenticating will make no difference.

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

405 Method Not Allowed
A request was made of a resource using a request method not supported by that resource.

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

407 Proxy Authentication Required (RFC 7235)
The client must first authenticate itself with the proxy.

408 Request Time out
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."

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

410 Gone
Indicates that the resource requested is no longer available and will not be available again. This should be used when a resource has been intentionally removed and the resource should be purged. Upon receiving a 410 status code, the client should not request the resource again in the future.

411 Length Required
The request did not specify the length of its content, which is required by the requested resource.

412 Precondition Failed (RFC 7232)
The server does not meet one of the preconditions that the client put on the request.

413 Request Entity Too Large
The request is larger than the server is willing or able to process.

414 Request-URI 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.

415 Unsupported Media Type
The request entity has a media type which the server or resource does not support. For example, the client uploads an image as image/svg+xml, but the server requires that images use a different format.

416 Requested Range Not Satisfiable (RFC 7233)
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.

417 Expectation Failed
The server cannot meet the requirements of the Expect request-header field.

418 I'm a teapot (RFC 2324)
This code was defined in 1998 as one of the traditional IETF April Fools' jokes, in RFC 2324, Hyper Text Coffee Pot Control Protocol, and is not expected to be implemented by actual HTTP servers. The RFC specifies this code should be returned by tea pots requested to brew coffee.

419 Authentication Time out (not in RFC 2616)
Not a part of the HTTP standard, 419 Authentication Time out denotes that previously valid authentication has expired. It is used as an alternative to 401 Unauthorized in order to differentiate from otherwise authenticated clients being denied access to specific server resources.

420 Method Failure (Spring Framework)
Not part of the HTTP standard, but defined by Spring in the HTTP Status class to be used when a method failed. This status code is deprecated by Spring.

421 Misdirected Request (HTTP/2)
The request was directed at a server that is not able to produce a response (for example because a connection reuse).

422 Unprocessable Entity (WebDAV; RFC 4918)
The request was well-formed but was unable to be followed due to semantic errors.

423 Locked (WebDAV; RFC 4918)
The resource that is being accessed is locked.

424 Failed Dependency (WebDAV; RFC 4918)
The request failed due to failure of a previous request (e.g., a PROPPATCH).

426 Upgrade Required
The client should switch to a different protocol such as TLS/1.0, given in the Upgrade header field.

428 Precondition Required (RFC 6585)
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 (RFC 6585)
The user has sent too many requests in a given amount of time. Intended for use with rate limiting schemes.

431 Request Header Fields Too Large (RFC 6585)
The server is unwilling to process the request because either an individual header field, or all the header fields collectively, are too large.

440 Login Time out (Microsoft)
A Microsoft extension. Indicates that your session has expired.

444 No Response (Nginx)
Used in Nginx logs to indicate that the server has returned no information to the client and closed the connection (useful as a deterrent for malware).

449 Retry With (Microsoft)
A Microsoft extension. The request should be retried after performing the appropriate action.

450 Blocked by Windows Parental Controls (Microsoft)
A Microsoft extension. This error is given when Windows Parental Controls are turned on and are blocking access to the given webpage.

451 Unavailable For Legal Reasons (Internet draft)
Defined in the internet draft "A New HTTP Status Code for Legally-restricted Resources". Intended to be used when resource access is denied for legal reasons, e.g. censorship or government-mandated blocked access.

451 Redirect (Microsoft)
Used in Exchange Active-Sync if there either is a more efficient server to use or the server cannot access the users' mailbox. The client is supposed to re-run the HTTP Auto-discovery protocol to find a better suited server.

494 Request Header Too Large (Nginx)
Nginx internal code similar to 431 but it was introduced earlier in version 0.9.4 (on January 21, 2011).

495 Cert Error (Nginx)
Nginx internal code used when SSL client certificate error occurred to distinguish it from 4XX in a log and an error page redirection.

496 No Cert (Nginx)
Nginx internal code used when client didn't provide certificate to distinguish it from 4XX in a log and an error page redirection.

497 HTTP to HTTPS (Nginx)
Nginx internal code used for the plain HTTP requests that are sent to HTTPS port to distinguish it from 4XX in a log and an error page redirection.

498 Token expired/invalid (Esri)
Returned by ArcGIS for Server. A code of 498 indicates an expired or otherwise invalid token.

499 Client Closed Request (Nginx)
Used in Nginx logs to indicate when the connection has been closed by client while the server is still processing its request, making server unable to send a status code back.

499 Token required (Esri)
Returned by ArcGIS for Server. A code of 499 indicates that a token is required (if no token was submitted).

5xx Server Error Codes:

These status codes indicate that it has encountered an error or is otherwise incapable of performing the request. These errors tend to be with the server itself, not with the request.

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

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).

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

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

504 Gateway Time out
The server was acting as a gateway or proxy and 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.

506 Variant Also Negotiates (RFC 2295)
Transparent content negotiation for the request results in a circular reference.

507 Insufficient Storage (WebDAV; RFC 4918)
The server is unable to store the representation needed to complete the request.

508 Loop Detected (WebDAV; RFC 5842)
The server detected an infinite loop while processing the request.

509 Bandwidth Limit Exceeded (Apache bw/limited extension)
This status code is not specified in any RFCs. Its use is unknown.

510 Not Extended (RFC 2774)
Further extensions to the request are required for the server to fulfil it.

511 Network Authentication Required (RFC 6585)
      The client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network (e.g., "captive portals" used to require agreement to Terms of Service before granting full Internet access via a Wi-Fi hotspot).

598 Network read time out error (Unknown)
This status code is not specified in any RFCs, but is 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 time out error (Unknown)
This status code is not specified in any RFCs, but is used by Microsoft HTTP proxies to signal a network connect timeout behind the proxy to a client in front of the proxy.

That's it.

If you are having difficulty to finding the code from this long list or don't want to read the whole bulky list, use the search (Ctrl + F).

Hope this list of HTTP error and status codes give you an clear idea that what's going wrong with the website your are trying to access.

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