Explanation of common HTTP status codes (200, 301, 302, 500, etc.)

For web site management workers there is a new word, HTTP status code, which is used to represent the Web server HTTP response status of the 3-digit code. The first number of a status code represents one of the five states of the response.

1XX Series: Specifies that the client should have certain actions that are accepted on behalf of the request and need to continue processing. Because no 1XX status codes are defined in the HTTP/1.0 protocol, the server prohibits sending a 1xx response to such clients unless under some experimental conditions.

2XX Series: The representative request has been successfully received, understood, and accepted by the server. The most common in this series are 200, 201 status codes.
200 Status code: Indicates that the request was successful and the desired response header or data body will be returned with this response
201 Status Code: Indicates that the request was successful and the server created a new resource, and its URI has been returned with the location header information. If the required resources cannot be established in time, the ' 202 Accepted ' should be returned.

202 Status code: The server has accepted the request but has not yet processed

3XX Series: Represents the need for the client to take further action to complete the request, these status codes are used for redirection, and subsequent request addresses (redirect targets) are indicated in the location domain of this response. The most common in this series are 301, 302 status codes.
301 Status Code: The requested resource has been permanently moved to a new location. When the server returns this response (a response to a GET or HEAD request), the requestor is automatically forwarded to the new location.

302 Status Code: The requested resource temporarily responds to the request from a different URI, but the requestor should continue to use the original location for future requests

304 The requested Web page has not been modified since the last request. When the server returns this response, the Web page content is not returned. If the page has not changed since the requestor last requested it, you should configure the server to return this response (known as the If-modified-since HTTP header).

4XX Series: Indicates a request error. Represents a client that may appear to have an error that interferes with the processing of the server. Common are: 401, 404 status Code.
401 Status Code: the request requires authentication. The server may return this response for pages that need to log on.
403 Status code: The server has understood the request, but refuses to execute it. Unlike the 401 response, authentication does not provide any help, and the request should not be repeated.

404 Status Code: The request failed and the requested resource was not found on the server. No information can tell the user whether the situation is temporary or permanent. If the server knows the situation, it should use the 410 status code to tell the old resources because of some internal configuration mechanism problems, has been permanently unavailable, and there is no jump to the address. 404 This status code is widely used when the server does not want to reveal exactly why the request was rejected or if no other appropriate response is available.

5XX Series: Represents the server in the process of processing the request error or abnormal state occurs, it is possible that the server is aware that the current hardware and software resources can not complete the processing of the request. 500, 503 status codes are common.
500 Status code: The server encountered an unexpected condition that caused it to not be able to complete the processing of the request. In general, this problem occurs when the server's code is wrong.
503 Status Code: The server is currently unable to process the request due to temporary server maintenance or overloading. Usually, this is a temporary state, a period of time will be restored
Understanding the basic SEO status code, SEO optimizer must have the knowledge. The HTTP status code is the language in which information is exchanged between the server and the client. By looking at the HTTP code of the website log, we can clearly see how the search engine crawls on the site.

Explanation of common HTTP status codes (200, 301, 302, 500, etc.)