When a visitor visits a web page, the visitor’s browser makes a request to the server where the page is located.

When the browser receives and displays a web page, the server where the web page resides returns a Server header containing an HTTP status code in response to the browser’s request.

Status code classification table

1 xx | Informational (Informational status code) to accept the request is processing

2 xx | Success (successful status code) to request processed properly

3 xx | Redirection (redirect) – the need for additional operation to complete the request

4 xx | Client error (Client) to the Client request, the server can’t process the request

5 xx | Server Error (Server Error) – > Server Error processing the request

Common HTTP status codes

200 The request is successful. It is usually used for GET and POST requests

204 indicates that the request sent by the client to the client is successfully processed, but the response message returned does not contain the body of the entity (no resources can be returned).

206 indicates that the client made a scope request and that the server successfully executed that part of the GET request

301 Permanent redirect: indicates that the requested resource has been assigned a new URL and the changed URL should be used afterwards

302 Temporary redirect: indicates that the requested resource has been assigned a new URL and is expected to use the new URL for this access

The difference between 301 and 302: the former is a permanent move, the latter is a temporary move (the URL may change later)

303 The requested resource has been assigned a new URL and should be directed to the requested resource using the GET method

Difference between 302 and 303: The latter explicitly states that clients should use GET to obtain resources

304 When a client sends a request with conditions (if-match, if-modified-since, if-none-match, if-range, or if-unmodified-since), the client sends a request with conditions (if-match, if-modified-since, if-none-match, if-range, or if-unmodified-since). The server allows access to the resource, but returns a status code if the request meets the condition

307 temporary redirect, which has the same meaning as 303, 307 will comply with the browser standards and not change from POST to GET; (This may vary by browser)

The current request cannot be understood by the server or the request parameters are incorrect

401 Without permission, HTTP authentication is required

403 Server denied this access (access permission is incorrect)

404 Server cannot find resource based on client request

503 The server is temporarily overloaded or is down for maintenance and cannot process requests