1xx Informational responses:
100 Continue: the server received the request headers, and the client should continue working with the requesting authority (if necessary, send a body, for example, a POST request). It would be inefficient to send a large request body to server after when the request was rejected for inappropriate headers. In order for the server to check the request headers, the client should send “Expect: 100-continue” as a header to its initial request and receive a “100 Continue” status response message in response to the sent body.
101 Switching Protocols: the requester has asked to switch the server to protocols and the server has agreed to do so.
102 Processing:a WebDAV query can contain many subqueries associated with file operations that require a long time to complete the request. This code indicates that the server received and processes the request, but there is no answer yet. This prevents the client from timeout and assumes that the request was lost.
103 Early Hints: this status code used to return some response headers before final HTTP message.
200 OK:it is a standard response for successful HTTP requests.
201 Created: the request was implemented, resulting in the creation of a new resource.
202 Accepted: the request was accepted for processing but not completed yet. As a result the request can or not be accepted when processing occurs.
203 Non-Authoritative Information (since HTTP/1.1): the server is a converting proxy (for example, a web accelerator) that received 200 OK from its source, but returns a modified version of the source response.
204 No Content:
the server successfully processed the request and does not return any content.
205 reset content: the server successfully processed the request, but is not returning any content. in contradistinction to 204 response, this response requires that the requester reset the document view.
206 Partial Content: the server provides only a portion of the resource (byte-service) because of the range header sent by the client. The range header is used by HTTP clients to resume intermittent downloads or load sharing into several simultaneous threads.
207 Multi status: the next message body is the default XML message and can contain several separate response codes, depending on how many sub-requests were made.
208 Already reported: the members of the DAV binding are already listed in the previous part of the answer (multi status) and are not included again.
226 IM Used: the server made a request for the resource, and the response is a representation of the result of one or more manipulations with instances applied to the current instance.
300 Multiple choices: specifies several resource parameters from which the client can choose (by matching the content with the agent). For example, you can use this code to represent multiple video format parameters, to display files with different file name extensions, or to suggest meaning values for a word.
301 Moved permanently: this and all future requests should be directed to the given URI.
302 Found: tells the client to browse another url. 302 has been superseded by 303 and 307. This is an example of industry practice contradicting the standard. The HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect (the original describing phrase was "Moved Temporarily"), but popular browsers implemented 302 with the functionality of a 303 See Other. Therefore, HTTP/1.1 added status codes 303 and 307 to distinguish between the two behaviors. However, some Web applications and frameworks use the 302 status code as if it were the 303.
303 See other: the response to the query can be found in another URI using the GET method. When it is received in response to POST (or PUT / DELETE), the client should assume that the server has received the data and must issue a new GET request to the given URI
304 Not modified: it reports that the resource has not been changed from the version specified by the If-Modified-Since or If-None-Match request headers. In this case, there is no need to re-transmit the resource, because the client still has a previously downloaded copy.
305 Use Proxy (since HTTP/1.1):the requested resource is available only through a proxy, the address for which 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. Originally meant "Subsequent requests should use the specified proxy".
307 Temporary Redirect (since HTTP/1.1): in this case, the request should be repeated with another URI; however, future requests should still use the original URI.
308 Permanent Redirect 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. So, for example, submitting a form to a permanently redirected resource may continue smoothly.
4xx Clients error
400 bad request: the server cannot or will not process the request because of an obvious client error, for example malformed request syntax, too large, invalid request message framing.
401 Unauthorized: 401 semantically means "unauthenticated", i.e. the user does not have the necessary credentials. Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided.
402 Payment Required: reserved for future use. The original intention was that this code might be used as a part of some form of digital cash or micropayment scheme, as proposed for example by GNU Taler, but that has not yet happened, and this code is not usually used. Google Developers API uses this status if a particular developer has exceeded the daily limit on requests.
403 forbidden: the request was valid, but the server is refusing action. The user might not have the necessary permissions for a resource, or may need an account of some sort.
404 not found: the requested resource can not be found, but may be available in the future. Possibly, requested by the client.
405 Method not allowed: a request method is not supported for the requested resource; for example, a GET request on a form that requires data to be presented via POST, or a PUT request on a read-only resource.
406 Not Acceptable: the requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request.
407 Proxy Authentication Required: the client must first authenticate itself with the proxy.
408 Request timeout: the server waiting time is out. 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 between multiple simultaneous updates.
410 Gone: indicates that the resource requested is no longer available and will not be available again. This shall be used when a resource was intentionally removed and the resource shall be purged. Upon receiving a 410 status code, the client should not request the resource in the future. Clients such as search engines should remove the resource from their indices. Most use cases do not require clients and search engines to purge the resource, and a "404 Not Found" may be used instead.
411 Length required: in 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 Payload too large:the request is larger than the server is willing or able to process.
414 URL 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 GET request in which case it would 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.
416 Range not feasible: 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.
418 I’m a teapot: 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 teapots requested to brew coffee. This HTTP status is used as an Easter egg in some websites, including Google.com.
421 Misdirected request: the request was directed at a server that is not able to produce a response.
422 Unprocessable entity: the request was well-formed but was unable to be followed because of semantic errors.
423 Locked:the resource that is being accessed is locked.
424 Failed Dependency: the request failed because it depended on another request and that request failed.
426 Upgrade required: the client should switch to a different protocol such as TSL/1.0 given in the header “Upgrade header” field.
428 Prediction required: the origin server requires that the request be conditional. It is designed to prevent the problem of a "lost update" when the client receives the status of the resource, modifies it and issues it back to the server when the third party changed the state on the server, which led to a conflict.
429 too many requests: the user has sent too many requests in a given amount of time.
431 Request header field too large: the server doesn’t want to process the request because either an individual header field, or all the.
451 Unavailable for legal reasons: 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.
5xx Server errors
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.
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 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.
507 Insufficient storage: the server is unable to store the representation needed to complete the request.
508 Loop detected: the server detected an infinite loop while processing the request.
510 Not extended: further extensions to the request are required for the server to fulfil it.
511 Network authentication required: the client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network.