What is http status code 400?

http status code 400 means that the domain name of the page being accessed does not exist or the request is incorrect. When the request sent by the client cannot be understood or processed by the server, the server will return a 400 status code. The 400 status code usually indicates the following situations: 1. Syntax error, which cannot be understood by the server; 2. Parameter error, the request contains parameters that cannot be processed by the server; 3. Request entity error, the request entity cannot be processed by the server; 4. For security issues, the server refuses to process; 5. The server refuses the request, and the server can refuse to process the request according to its own policy.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

HTTP status code 400 refers to a client request error. When the request sent by the client cannot be understood or processed by the server, the server will return a 400 status code.

400 status code usually indicates the following situations:

Syntax error: The request sent by the client may have syntax errors and cannot be understood by the server. For example, the URL format in the request is incorrect, the request header information is incorrect, the request method is incorrect, etc.

Parameter error: The request sent by the client contains parameters that the server cannot process. For example, required parameters are missing, parameter values ​​are illegal, parameter types are wrong, etc.

Request entity error: The request entity sent by the client (such as the data in the request body) cannot be processed by the server. For example, the request body format is incorrect, the request body size exceeds the limit, etc.

Security issue: The request sent by the client may have security issues, and the server refuses to process it. For example, unauthorized access, authentication failure, etc.

The server rejects the request: The server can refuse to process the client's request according to its own policy. For example, the server may limit the frequency of requests, the requested content may not meet the server's requirements, etc.

When the server returns a 400 status code, detailed error information is usually included in the response message body so that the client can understand the specific cause of the error. The client can handle the returned error information accordingly to repair the request or display the error information to the user.

In order to avoid 400 errors, the client should try to follow the specifications of the HTTP protocol when sending requests. Ensure that the syntax of the request is correct, the parameters are legal, the requesting entity meets the requirements, and necessary authentication information is provided. If the client receives a 400 error, it should first check whether there is a problem with its request and then make corresponding repairs.

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