Tips and tricks to diagnose and debug a 400 Bad Request error

Here you can find a list of the most common error messages that users have reported while facing a 400 Bad Request error:

  • Bad Request - Invalid URL
  • Bad Request: Error 400
  • HTTP Error 400 - Bad Request
  • HTTP Error 400. The request hostname is invalid
  • Bad Request. Your browser sent a request that this server could not understand

There’s a variety of issues that can lead to a 400 Bad Request error. Here are a few ways to troubleshoot this error

How to fix a 400 Bad Request?

It’s hard not to be unfazed by an HTTP error that tells you little about the problem. That said, fixing a 400 Bad Request error takes just a few steps. We’ve put together a few useful tips below to help you find your way out.


A 400 Bad Request error is usually a client-side error. A good case in point is a URL string syntax error. Incorrectly typed URLs, or URLs that contain backslashes, spaces and other invalid characters can generate a 400 request.

Example with correct URL:

Example with an added space and your browser will throw a 400 Bad Request error:

2. Check your internet connection

If you keep seeing a 400 Bad Request on nearly every website you visit, check your internet connection or consult your internet service provider to rule out a poor connection.

3. Clear browser cookies

A website may fail to comply with your request due to old or corrupt cookies. As a quick fix, consider clearing your browser cache and cookies. Repeat this exercise from time to time to avoid running into a 400 Bad Request error.

4. Clear DNS Cache

This works similar to clearing browser cookies and cache, except that it’s locally stored in your computer and may contain outdated information that doesn’t sync with the current webpage. You can clear old DNS information and records from your system within the Command Prompt in Windows and Mac.

Important Note: Here is a great article for how to clear your cache and cookies

5. Compress the file

If you run into an HTTP Error 400 right after uploading a file, try uploading a smaller file. If that works, you may conclude that the initial file exceeded the server limit. The best workaround for uploading a large file is to compress it. Most websites permit zip files that fall under the maximum upload size.

6. Deactivate browser extensions

While this isn’t a common solution for a 400 Bad Request error, some browser extensions may interfere with cookies. Temporarily disabling them might resolve the problem.

7. Restart your system

If all other methods fail, restart your computer system and attached peripherals, such as routers. If this doesn’t resolve the problem, the error is likely a server-end issue, and the website administrator should fix it soon.

You can also contact the host to report the problem. Chances are, they’re already aware of the problem or outage and are working on it.

If you have any questions about this, please contact our support team by clicking the support icon in the bottom right-hand corner of this page.

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