HTTP status Code

One, 1XX

The class status code information indicates: a temporary response. Clients should be prepared to receive one or more 1XX responses before they receive a regular response

100	Continue	The initial request has been accepted and the customer should continue to send the remainder of the request. (HTTP 1.1 new)	The client should continue to send the request. This temporary response is used to inform the client that some of its requests have been received by the server and are still not rejected. The client should continue to send the remainder of the request, or ignore the response if the request has been completed. The server must send a final response to the client after the request is complete.
101	Switching protocols	The server translates the client's request to another protocol (HTTP 1.1 new)	The server has understood the client's request and will notify the client via a upgrade message header that a different protocol is being used to complete the request. After the last empty line of the response is sent, the server switches to those protocols defined in the upgrade message header. Similar measures should be taken only when switching to a new protocol is more beneficial. For example, switching to a new HTTP version is more advantageous than an older version, or switching to a real-time, synchronized protocol to deliver resources that exploit this type of feature.
102	Processing		The status code that is extended by WebDAV (RFC 2518), on behalf of processing, will continue to execute.

Second, 2xx success

OK

204 No Content: request processing succeeds, but no resources can be returned

The request was processed successfully, but the body part of the entity was not included in the returned response message

206 Partial Content: Request for part of a resource

The response message contains the entity content specified by the Content-range range

Third, 3xx redirection

301 Moved Permanently: Permanent redirect

Indicates that the requested resource has been assigned a new URI and should later use the URI that the resource now refers to

302 Found: Temporary redirection

Indicates that the requested resource has been assigned a new URI and that the user will be able to access it using the new URI

303 See other

Indicates that there is another URI for the resource that corresponds to the request and that the requested resource should be directed with the Get method

(303 and 302 have the same functionality, but 303 explicitly indicates that the client should use the Get method to get the resource, which is the difference between the two)

* * When the 301/302/303 response status code returns, almost all browsers will change the post to get, and delete the principal within the request message, and then the request will be sent again automatically

304 Not Modified: no relationship with redirection

Indicates that when a client sends a request with a condition, the server side allows the request to access the resource but does not meet the condition.

304 when returned, does not contain the body part of any response

* A conditional request means that a request message with a Get method contains any header in the If-match,if-modified-since,if-none-match,if-range,if-unmoidfied-since

307 Temporary Redirect: temporary redirection

And 302 have the same meaning. Although the 302 standard prohibits post from being converted to get, it is not observed when used in practice;

307 will follow the browser standard and will not change from post to get.

Four, 4xx client error

Request

Indicates that there is a syntax error in the request message. When an error occurs, you need to modify the requested content and send the request again

401 Unauthorized

Indicates that a request for sending requires authentication information that is authenticated by HTTP, and when the browser first accepts a 401 response, it pops up the Authentication dialog window.

403 Forbidden

Indicates that access to the requested resource was rejected by the server (access to the file system was not granted, an unauthorized sending source IP address was attempted to access, etc.)

404 Not Found

Indicates that the requested resource could not be found on the server (can also be used when the server side denies the request and does not want to explain the reason)

Five, 5xx server error

Internal Server Error

Indicates that a server-side error occurred while executing the request (there could be a bug in the Web app or some temporary failure)

503 Service Unavailable

Indicates that the server is temporarily overloaded or is undergoing downtime maintenance and cannot process requests now.

HTTP status Code