The following is a list of commonly used and returned HTTP response status codes that a website can return. This includes codes from IETF internet standards as well as RFCs status codes that have not been standardized. These codes are valuable for SEO when determining if the pages are returning the correct header code to Google and other search engines so they (the search engines) can crawl them properly and attribute metrics.
What does a HTTP status code in the 100 range mean? Request received, continuing process.
100 Continue: This means that the server has received the request headers, and that the client should proceed to send the request body.
101 Switching Protocols: This means the requester has asked the server to switch protocols and the server is acknowledging that it will do so.
102 Processing: 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.
What does a HTTP status code in the 200 range mean? This class of status codes indicates the action requested by the client was received, understood, accepted and processed successfully.
200 OK: Standard response for successful HTTP requests. The actual response will depend on the request method used. In a GET request, the response will contain an entity corresponding to the requested resource. In a POST request the response will contain an entity describing or containing the result of the action.
201 Created: The request has been fulfilled and resulted in a new resource being created.
202 Accepted: The request has been accepted for processing, but the processing has not been completed.
203 Non-Authoritative Information: 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.
205 Reset Content: The server successfully processed the request, but is not returning any content. This response requires that the requester reset the document view.
206 Partial Content: The server is delivering only part of the resource due to a range header sent by the client.
207 Multi-Status: 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.
What does a HTTP status code in the 300 range mean? This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request.
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, or word sense disambiguation.
301 Moved Permanently: This and all future requests should be directed to the given URI.
302 Found: This is the most popular redirect code, but also an example of industrial practice contradicting the standard. HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect, but popular browsers implemented 302 with the functionality of a 303 See Other.
303 See Other (since HTTP/1.1): The response to the request can be found under another URI using a GET method. When received in response to a PUT, it should be assumed that the server has received the data and the redirect should be issued with a separate GET message.
304 Not Modified: Indicates the resource has not been modified since last requested.
305 Use Proxy: Many HTTP clients do not correctly handle responses with this status code, primarily for security reasons.
306 Switch Proxy: No longer used.
307 Temporary Redirect (since HTTP/1.1): In this occasion, the request should be repeated with another URI, but future requests can still use the original URI. For instance, a POST request must be repeated using another POST request.
4xx Client Error
What does a HTTP status code in the 400 range mean? The 4xx class of status code is intended for cases in which the client seems to have erred. The server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition.
400 Bad Request: The request cannot be fulfilled due to bad syntax.
401 Unauthorized: Similar to 403 Forbidden, but specifically for use when authentication is possible but has failed or not yet been provided.
402 Payment Required: The original intention was that this code might be used as part of some form of digital cash or micro-payment scheme.
403 Forbidden: The request was a legal request, but the server is refusing to respond to it.
404 Not Found: The requested resource could not be found but may be available again in the future.
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.
408 Request Timeout: The server timed out waiting for the request.
409 Conflict: Indicates that the request could not be processed because of conflict in the request, such as an edit conflict.
410 Gone: Indicates that the resource requested is no longer available and will not be available again.
411 Length Required: The request did not specify the length of its content, which is required by the requested resource.
412 Precondition Failed: The server does not meet one of the preconditions that the requester 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.
415 Unsupported Media Type: The request entity has a media type which the server or resource does not support.
416 Requested Range Not Satisfiable: The client has asked for a portion of the file, but the server cannot supply that portion.
417 Expectation Failed: The server cannot meet the requirements of the Expect request-header field.
422 Entity Cannot Be Processed: The request was well-formed but was unable to be followed due to semantic errors.
423 Locked: The resource that is being accessed is locked
424 Failed Dependency: The request failed due to failure of a previous request.
425 Unordered Collection : Defined in drafts of “WebDAV Advanced Collections Protocol”, but not present in “Web Distributed Authoring and Versioning (WebDAV) Ordered Collections Protocol”.
426 Upgrade Required: The client should switch to a different protocol such as TLS/1.0.
449 Retry With: The request should be retried after performing the appropriate action.
450 Blocked by Windows Parental Controls: This error is given when Windows Parental Controls are turned on and are blocking access to the given web page.
5xx Server Error
What does a HTTP status code in the 500 range mean? Response status codes beginning with the digit “5″ indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request.
500 Internal Server Error A generic error message, given when no more specific message is suitable.
501 Not Implemented: The server either does not recognize the request method, or it lacks the ability to fulfill the request.
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.
504 Gateway Timeout: 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: Transparent content negotiation for the request results in a circular reference.
509 Bandwidth Limit Exceeded: This status code is not specified in any RFCs.
510 Not Extended (RFC 2774): Further extensions to the request are required for the server to fulfill it.