400 Faulty Requests (Bad request)

What is a 400 Bad Request error?

Status code 400 Bad Request means that the server cannot process the request due to an error on the client side. Servers usually return this error when they find that the request is faulty, wrongly formatted, or contains invalid information.

The most common causes include improperly formatted requests, excessive headers or cookies, damaged cookies, invalid request messages, and in some cases server configuration issues.

Error 400 Bad Request belongs 4xx series of HTTP status codes, which denotes errors on the client side:

• 4 – denotes client error
• xx – provides additional information on the type of error

Other common 4xx errors include:

• 403 Forbidden – The server understands the request but refuses authorisation
• 404 Not Found – The requested resource does not exist on the server
• 410 Gone – Resource requested permanently removed
• 451 Unavailable for Legal Reasons – Resources not available due to legal constraints

Common Causes of Error 400 Bad Request

Since error 400 is a general client error, it is sometimes difficult to accurately determine the cause. However, the most common reasons include:

1. Too large request size

Servers often have limitations on the size of requests they can process. If the request exceeds this limit, the server can reject it and return the 400 error.

For example, if the server allows uploading up to 5 MB, an attempt to send a 10 MB file may result in a 400 error.

2. Incorrectly formatted URL

Malformed URL contains syntactic errors such as missing, invalid or unsupported characters.

Examples of incorrect URLs:

• yourdomain..com (two points)
• yourdomain.com/best yoga

Such URLs most often cause a 400 Bad Request error.

3. Unsupported HTTP methods

Servers only support certain HTTP methods. The most common methods such as GET, POST, PUT i DELETE are supported on most servers.

If the client tries to use the HTTP method that the server does not recognize or support, there may be an error of 400.

For example, some configurations support the method PURGE, while many servers do not support it.

4. Damaged cookies

Cookies are used to store session data and other information between the client and the server. If cookies are damaged, shortened or contain invalid characters, the server may refuse the request and return the 400 error.

5. DNS (Domain Name System) issues

Although DNS rarely directly causes an error of 400, problems with DNS can contribute to it.

Examples include:

• Irregularly formatted DNS requests
• Inability of the server to contact the DNS server
• Temporary difficulties in the operation of DNS servers

6. Server configuration problems

In some cases, the problem may be in the server itself. Wrong route settings, request processing or security rules can cause an error of 400 even when the request is sent correctly.

How to Solve an Error HTTP 400 Bad Request

The solution depends on the cause of the error, but the following steps can help solve the most common problems:

1. Clear browser cookies

Damaged cookies are a common cause of error 400. Clear your browser's cookies and cache and try to open the page again.

2. Check and correct the URL

Carefully check the URL for tipfelers and syntactic errors such as spaces, missing hairlines or wrong domains. The URL must be properly formatted.

Special characters need to be encoded correctly (UTF-8):

• Distance →
• & →
• = →
• ? →

Example:

yourdomain.com/yoga poses → yourdomain.com/yogaposes

3. Remove invalid characters

Check the request and remove any invalid or incorrectly formatted characters in the URLs, headers, and authority of the request. Using standard characters and proper encoding reduces the possibility of an error of 400.

4. Reduce the size of the request

Check the server documentation to find out the maximum allowed request size. If necessary, reduce file size by compression, removing unnecessary data, or dividing the request into smaller units.

5. Use supported HTTP methods

Make sure that the request uses the HTTP method supported by the server for a specific endpoint. Review the API or server documentation and adjust the request if necessary.

6. Include all required HTTP headers

Make sure that the request contains all mandatory HTTP headers, such as Authorization or Content-Type, if needed. Find information about the required headers in the server documentation.

7. Check and fix problems on the server

If the 400 error still appears despite the correct client requirements, it is necessary to check the server configuration. View route rules, content processing settings, and security restrictions that may prevent valid requests from being processed.