Understanding 400 Bad Request Error: What are its Causes and How to Fix it

Understanding 400 Bad Request Error: What are its Causes and How to Fix it

What is 400 Bad Request Error? 

The 400 Bad Request error is an HTTP status code that happens when the server can’t understand or process the request made by the client (often from a web browser). This occurs due to requests with wrong syntax or missing important information needed by the server to fulfill the request. Users see this error message when trying to access a webpage, submit a form, or interact with a web application facing this issue. 

To fix the problem, you usually need to identify and resolve the specific request causing the error. Unfortunately, the 400 Bad Request error doesn’t give detailed information about the exact nature of the problem, so troubleshooting is necessary. 

In this blog, we’ll take you through how you see 400 Bad Request error on different browsers, the causes of the error and how to fix the same. 

400 Bad Request Error on different browsers 

Similar to a 404-error page, the 400 Bad Request page can be customized. For instance, Google has its own custom 400 Bad Request page that appears the same on all web browsers. 

If a website doesn’t have its customized error page, the web browser will display the default one. Here’s how the HTTP 400 Bad Request status code looks on different browsers: 

  • Mozilla Firefox 

When attempting to access a website using incorrect syntax, Mozilla Firefox will display a blank page. Unlike some other browsers, there is no explicit text indicating that you have encountered an HTTP 400 Bad Request error. This absence of specific error messaging can make identifying the problem more challenging for users. 

  • Google Chrome 

When encountering a 400 Bad Request Error in Chrome, the browser will display an error icon alongside the message “The page isn’t working.” Below that, you will see the suggestion, “If the problem continues, contact the site owner.” At the bottom of this message, you will find the HTTP ERROR 400 notification. 

  • Microsoft Edge 

Microsoft Edge’s design closely resembles that of Google Chrome, featuring an almost identical layout with the “HTTP ERROR 400” text displayed at the bottom. 


Causes of the 400 Bad Request Error 

When a hosting server returns a 400 Bad Request error, it signifies that it cannot understand or process your request. Below are common causes of the 400 Bad Request error: 

Invalid URL syntax: Mistyped URL or invalid characters in the URL. 

Corrupted browser cache or cookies: Expired cookies or corrupted cache preventing proper request processing. 

Conflicting browser extensions: Browser extensions interfering with the request. 

Bad DNS cache: Locally cached DNS data out of sync with the current DNS registration for the domain. 

Large uploaded file size: Uploading a large file that exceeds the maximum upload limit. 

It’s also possible for a 400 HTTP error to result from a server-side error, such as misconfigured servers or temporary glitches on the website.


How to Fix a 400 Bad Request Error 

Follow the steps provided in this section to diagnose and resolve a 400 Bad Request error. The recommended solutions include:

1.Check the submitted URL 

One of the common causes of a 400 Bad Request error is the URL string. Check for correct spelling, proper separation with forward slashes, and proper encoding of special characters. Consider using an online URL encoder/decoder for long URLs. If the error persists, clearing the cache may be necessary. 

2.Clear browser cookies 

If clearing the browser cache didn’t work, delete cookies too. A single website can use numerous cookies, and if even one is expired or corrupted, it can trigger a 400 Bad Request error.  

In Chrome, open the Clear browsing data window by clicking the three dots icon. 

Then, go to More Tools > Clear Browsing Data. Check Cookies and other site data and select ‘All times’ to delete all website cookies. Reloading the website might resolve the error associated with corrupt or expired cookies.  

3.Check if file upload exceeds the server limit 

If the file you’re uploading exceeds the size limit of a website server, a 400 Bad Request error may occur. To test this, try uploading a smaller file first. If it succeeds, the initial file is likely too large, requiring compression before uploading. Numerous online resources are available to help compress large images, videos, and audio files based on the file type. 

4.Clear DNS cache 

Local DNS lookup data becoming corrupted or outdated is another frequent cause of a 400 Bad Request error. Unlike browser-stored data, the operating system itself handles local DNS data. To address this issue, consider clearing the local DNS cache to ensure accurate and up-to-date data retrieval. 

READ: What Is a Nameserver and Why Is It Important? 

 5.Deactivate browser extensions 

If you have browser extensions that impact website cookies, they might be causing the issue. Temporarily disable them and check if it resolves the problem before attempting to connect to the website again. It’s a step worth trying, especially if you’ve explored all other options.



Fixing the 400 Bad Request error is easy with the right tips. All you need to do is understand the causes and apply the right solutions to resolve this issue. Check URLs, headers, and request data for proper transmission. Clear cache, update browsers, and review server settings. Use best practices and debugging tools for a smoother browsing experience and better web development, ensuring a seamless online journey for everyone.


FAQs on 400 Bad Request 

What are some best practices for avoiding a 400 Error?  

To avoid a 400 Bad Request error, follow these best practices: validate user input to prevent malformed requests, ensure proper URL encoding, include necessary request headers, use proper HTTP methods, and implement proper error handling with clear error messages.


Are there any tools that can help me debug a 400 Error?  

Indeed, numerous tools are available to aid in debugging a 400 Bad Request error. Browser developer tools and server log analysis tools like Apache Log Viewer or ELK Stack can effectively identify the error’s underlying cause and offer valuable insights for its resolution.

If you have any queries or suggestions feel free to leave them in the comments box below!


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