What is a 400 Bad Request?
The 400 Bad Request status code indicates the server will not process the request because of a client error. Servers typically return a 400 Bad Request error code when they identify an issue from the client’s end.
For example, an improperly formatted request, oversized headers/cookies, corrupted cookies, invalid request messages, and even server issues can cause a server to return a 400 Bad Request.
The 400 Bad Request error belongs to the 4xx series of HTTP status codes.
- 4 indicates the error is a client error
- xx is a placeholder for two numbers that provide additional information about the status of the HTTP request
Other common 4xx series errors include:
- 403 verboden: Indicates the server understands the request but refuses to authorize it
- 404 Niet Gevonden: Indicates the requested resource was not found on the server
- 410 Weg: Indicates the requested resource has been permanently deleted from the web
- 451 Unavailable for Legal Reasons: Indicates the requested resource was removed due to legal restrictions
Causes of the 400 Bad Request Error
The HTTP 400 Bad Request is a broad error that could result from various reasons. So it can be hard to determine the specific cause. However, some common causes include:
1 Large Request Size
Many servers have limits on the size of the requests they will process. When a client sends a request that exceeds this limit, the server can reject it and return a 400 Bad Request error.
For example, if a server has a request limit of 5 MB, it will return a 400 Bad Request error when the browser sends a request to upload a 10 MB file.
2 Malformed URL
A malformed URL refers to a URL containing syntax errors, such as missing, incorrect, or unsupported characters. For example, malformed URLs like yourdomain..com (double dots) and yourdomain.com/best yoga (a space) will return a 400 Bad Request error.
3 Unsupported HTTP Methods
Servers support specific HTTP methods. The most common ones, like GET, PUT, POST, and VERWIJDEREN are supported by most servers. However, when a client attempts to use an HTTP method that the server does not recognize or support, it can trigger a 400 Bad Request error.
For example, some servers support the PURGE method, while many do not. While the method would work on supporting servers, it will return a 400 Bad Request error on an unsupported one.
4 Corrupted Cookies
Cookies are used to store session information and other data between the client and server. If these cookies are truncated, corrupted, or contain invalid characters, they can cause the server to reject incoming requests and return a 400 Bad Request error.
5 Domain Name System Server Issues
Servers rely on domain name system (DNS) servers to convert domain names into IP addresses. However, while the DNS server rarely causes 400 errors by itself, such errors could occur when there are issues with the request.
Bijvoorbeeld, improperly formatted DNS server requests can cause the 400 Bad Request error. 400 errors can also occur when the server cannot contact the DNS server or the DNS server is experiencing issues.
6 Server Configuration Issues
Sometimes, the server itself may be misconfigured. In such instances, the server can fail to handle the request and will return a 400 Bad Request status code error, even when the request is properly configured.
How to Fix the HTTP 400 Bad Request
The specific solution to fixing the HTTP 400 Bad Request can vary, depending on the cause. However, here are some general tips to fix common issues that could cause the error.
1 Clear Your Browser Cookies
Corrupt cookies can cause the 400 Bad Request error. If you are a web user, clear your browser cache and try accessing the URL again.
2 Review and Correct URL Errors
Review the URL for typos and syntax errors, such as missing slashes and incorrect domain names. You should also ensure the URL follows the standard URL structure, proper formatting rules, and best practices.
For example, special URL characters should be encoded using UTF-8. In such cases, spaces should be encoded as %20, & should be %26, = should be %3D, and ? should be %3F. So a URL like yourdomain.com/yoga poses should be encoded as yourdomain.com/yoga%20poses.
3 Remove Invalid Characters
Review and remove every invalid character in your request. This includes the invalid, unrecognized, and improperly formatted characters in your request URLs, headers, and body. Make sure to use standard characters and proper encoding, as they reduce the chances of the server returning a 400 Bad Request error.
4 Reduce the Request Size
Consider reducing your request file. To get started, check the server’s documentation for request size limits. Once done, you can reduce your request file size by compressing it, removing unnecessary data, or breaking it into smaller chunks.
5 Use Supported HTTP Methods
Ensure that the HTTP method used in the request is supported by the server for the specific endpoint you are trying to access. Review the API documentation or server configurations to confirm which methods are allowed, and if you previously used an unsupported method, modify your request to include a valid HTTP method.
6 Include All Required Headers
Ensure your request contains all required HTTP headers. For example, some servers require requests to include an Authorization or Content-Type header. So, review the server documentation to identify its header requirements. Once done, include them in your request.
7 Fix Any Server Issue
If the 400 Bad Request error persists even with correct client-side requests, it may be necessary to review server configurations. Check the server’s routing rules, content handling settings, and any limitations that may block the server from processing valid requests.