What is an HTTP 400 Status Code?

In the realm of web development, HTTP status codes play a crucial role in communicating the results of client-server interactions. One of the most common, yet often misunderstood, is the HTTP 400 status code, known as “Bad Request.”

What is an HTTP 400 Status Code?

An HTTP 400 status code indicates that the server cannot process the request due to a client-side error. Unlike server-side errors that typically return codes in the 500 range, a 400 error points to an issue with the client’s request itself. This could be due to various reasons such as malformed syntax, invalid request message framing, or deceptive request routing.

Common Causes of HTTP 400 Errors

  1. Malformed Request Syntax: One of the primary causes of a 400 Bad Request is incorrect syntax. This can happen if the request line is not formatted correctly or if the request headers contain improper data.
  2. Invalid Query Parameters: When a client sends parameters that the server cannot understand or process, a 400 error may be returned. This often occurs with malformed URLs or unsupported query parameters.
  3. Oversized Request: If the request is too large for the server to handle, it might reject it with a 400 status code. This can be due to exceeding header size limits or the overall request payload being too large.
  4. Incorrect Content Types: If the content-type of the request is not supported by the server, or if the server expects a different BTC Users Number format, a 400 error can be the result.

Troubleshooting HTTP 400 Errors

To resolve a 400 Bad Request, first inspect the request syntax and ensure it adheres to the correct format. Verify that  all new zealand phone number headers, query parameters, and payloads are valid and supported by the server. Additionally, checking the server’s logs can provide insights into the specific nature of the problem.


Understanding HTTP 400 status codes is essential for diagnosing client-side issues in web interactions. By pinpointing the exact cause of these errors, developers can create more robust and user-friendly applications. Whether it’s a malformed URL or an unsupported header, addressing 400 errors promptly ensures smoother communication between clients and servers.

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