Detailed explanation of status code meaning

Status code

1、 Definition

When users are browsing the web , The browser will return a htttp Status code , It is mainly used to respond to browser requests . Usually , It's usually 3 Digit number ,http The status code is from RFC 2616 To define the , The first number of all the status codes represents the status .

2、 Classification of status codes

1xx
This type of status code , The representative's request has been accepted , Need to continue processing . This kind of response is a temporary response , Contains only the status line and some optional response header information , And end with a blank line .

2xx
This type of status code , The delegate request has been successfully received by the server 、 understand 、 And accept .

3xx
This kind of status code represents that the client needs to take further actions to complete the request . Usually , These status codes are used to redirect , Subsequent request address （ Redirect to ） In this response location The domain indicates .

4xx
This type of status code represents what appears to be an error on the client side , Hinders server processing . Unless the response is a HEAD request , Otherwise, the server should return an entity that explains the current error condition , And whether it's temporary or permanent . These status codes apply to any request method . The browser should show the user any entity content contained in such an error response .

5xx
This kind of status code represents that the server has an error or abnormal status in the process of processing the request , It is also possible that the server realizes that it cannot complete the processing of the request with the current hardware and software resources . Unless it's a HEAD request , Otherwise, the server should contain an entity explaining the current error status and whether the status is temporary or permanent . The browser should show the user any entities included in the current response .

3、http What are the common status codes

200
HTTP 200 The status code indicates that the request was successful , And the request sent wants to return a response , If you are visiting the website or checking the website space log , notice 200 It means normal .

301
HTTP 301 The status code may not be very strange to the operation and maintenance personnel , Generally, when a website jumps , use 301, In general , Because the domain name expires , Or do not renew the domain name , Transfer resources to other websites ,301 Is a permanent redirection .

302
HTTP 302 Status code is HTTP A status code in the protocol (Status Code). It can be simply understood that the resource does exist , But it has been temporarily changed ; In other words , That is, the requested resources are temporarily resident in different URI Next , Therefore, unless a cache header indication is specified , The status code is not cacheable .

304
If the client sends a conditional GET Request and it has been allowed , And the content of the document （ Since last visit or as requested ） It hasn't changed , Then the server should return this 304 Status code . The simple expression is ： The server has executed GET, But the file has not changed .

307
307 For temporary redirection , If redirection 307 The original request of is not get perhaps head Method , Then the browser will automatically redirect , Even if location Yes url, It should also be ignored .

Status code 307 And 302 The only difference between is , When sending a redirect request ,307 The status code ensures that the request method and message body will not change . When the response status code is 302 When , Some old user agents will incorrectly convert the request method to GET： Use non GET Request method and return 302 Status code ,Web The health of the application is unpredictable ; And back 307 The status code is predictable . about GET The request for , There is no difference between the two situations .

308
stay HTTP Agreement ,308 Permanent Redirect( Permanent redirection ) Is the response status code for redirection , Indicates that the requested resource has been permanently moved to by Location The first part specifies URL On . The browser will redirect , At the same time, the search engine will also update its links ( use SEO In Chinese jargon , intend “ Link juice ”(linkjuice) Passed to the new URL)

400
HTTP 400 The status code tells the client that it sent an exception request .400 A page is when a user opens a web page , Return to the user interface with 400 Prompt page . It means that the domain name of the page you visit does not exist or the request is wrong . There are two main types .

401
Request for authentication . For the web page requested after login , The server may return this response .

403
Server rejects request . If you are in Googlebot See this status code when trying to grab a valid page on your website （ You can go to Google Webmaster tool diagnosis under the network crawl page to see this information ）, Maybe your server or host rejected Googlebot visit .

404 Status code
When users are visiting the website , There may be 404 page , appear 404 The reason for the page may be that the requested resource does not exist , The page may be deleted .

500
HTTP 500 Status code is also the most common status code , I believe many programmers have encountered ,500 Indicates that there is a problem with the server of the website , But different status codes represent different problems in the server .

501
The server does not have the function to complete the request . for example , This code may be returned when the server does not recognize the request method .

503
The server is currently unavailable （ Maintenance due to overload or shutdown ）. Usually , It's just a temporary situation .

reference ：https://www.liujason.com/old-blog/1406.html