How To Fix 400 Bad Request: Request Header Or Cookie Too Large?

Have you ever seen a "400 Bad Request" error while browsing on the web, that might be confusing for you about what it means? When you request to a website the server responds with an HTTP status code.

This error is among the responses in terms of the HTTP status code used by web servers in order to communicate with your browser. HTTP Status Codes that are commonly used are: 200 OK, 404 Not found, and 500 Internal Server Error.

What is a "400 Bad Request Error"?

A "400 Bad Request Error" is a way in which the server says that it is having trouble understanding the request sent to it. It is simply a signal through which the server tells that something is wrong with the request sent to it. In order to tell the end user that the server is facing issues, the server sends 400 Bad Request Error.

The "Request Header or Cookie Too Large" part tells that the problem being faced is especially with the size of the request headers or cookies.

Common Causes of Error

• Large Cookies: Cookies are small pieces of data that websites store on your computer. They help you remember things like your login credentials. Sometimes, websites store a lot of information in cookies. If this information becomes too big it can cause problems, when your browser tries to send them to the server.
• Excessive Request Headers: Request Headers are the information that your browser sends to the server along with the request. If your browser sends too many headers in such a case server might not be able to handle them.
• Redirect Loops: Imagine Page A redirects you to Page B and Page B redirect back to Page A this is called redirect loops. This can cause the size of the request to grow too large as if the browser follows the redirects it keeps on adding data which can increase the size.
• Server Configuration Limits: Sever limits are very low, it might not be able to process larger requests. Think of a filing cabinet is like a server with a limited number of drawers in it. If you try to stuff too many files at once in it, the cabinet will not be able hold everything and will start rejecting new files.
• DNS Cache Issues: Your website keeps a small memory of website addresses called DNS Cache.Sometimes, this information in the cache can become outdated and incorrect. When your computer tries to visit a website using this bad information, ut ca confuse the server, causing errors.
• Server Restrictions: When you visit a website, your browser sends information to the server, including data about your session, preferences,or history. If this information is too large - because of big cookies, too many headers or both - the server may refuse to accept request, causing the error.

How to Fix the Error?

Clear your Browsing Cookies

Clearing you cookies can resolve the error if they have become too large. These can be resolved through-

1. Google Chrome

For resolving the error using Google Chrome-

• Click on three dots( menu) in the top right corner and then go to settings.
• Cick on 'Privacy and Settings' and select 'Clear Browsing Data' .
• Check Cookies an other site and Cached images and files.
• At last, click on Clear data.

2. Morzilla FireFox:

For clearing cookies using Morzilla Firefox -

• Click on three lines in the top-right corner and then go to settings.
• Select Privacy and Security.
• At last, click Clear Data under the Cookies and Site Data section.

Reduce Cookie Size

Larger cookies can cause the server to reject the request. Reduce the amount of data which is stored in cookies. To do that you need to review the data storage and ensure cookies only store essential information in it. If your cookies is having lot of information, cut it down and keep only the relevant information and discard remaining in order to reduce cookie size.

Example:

Before:

document.cookie = "preferences=theme:dark;userID:12345;otherData:moreData;expires=Fri, 31 Dec 9999 23:59:59 GMT"; 

After:

document.cookie = "preference =theme:dark;expires=Fri,  31 Dec 9999 23:59:59 GMT";

In the above example, we have removed extra information in order to reduce cookie size.

Limit Custom Headers

Limiting Custom Headers can fix this error as too many or excessively large headers can overlead the sever. In order to fix this issue, you should review and reduce the header by checking if you are sending unnecessary headers or if any headers are too large.If you are using browsers extensions that add extra headers disable or remove such extensions.

Syntax:

Before (with extra headers)

fetch('/data', {
  headers: {
    'X-Custom-Header': 'ExtraData',
    'Another-Header': 'MoreData',
    'Cookie': 'sessionID=123456; trackingID=7890'
  }
});

After( with reduced Headers)

fetch('/data', {
  headers: {
    'Cookie': 'sessionID=123456'
  }
});

In the before example, the request includes extra custom headers and a tracking cookie that might not be needed. In the After example, we keep only the essential cookie.

Reset Browser Settings

Sometimes, browser settings or extensions can interfere with how requests are handled. Resetting the browser settings can help us in resolving this issue. For this you have to -

• Open your Browser: Open the browser where you facing this issue.
• Go to Settings: Access the Settings Menu.
• Find Advanced Settings: Search for an Option as Advanced Settings or reset settings.
• Choose Reset: Look for "Reset Settings" or "Restore Settings to their original defaults" option.
• Confirm and Restart: Click on Confirm and then restart your browser.

Flush DNS Cache

The 400 Bad Request error indicates that the server has received a request with headers or cookies that exceed its allowed limits. This can be often be due to outdated or corrupted data.Flushing the DNS cache clears outdated or corrupted DNS records that might affect your browsing experience, which can sometimes resolve issue related to web requests or headers. In order to Flush DNS in windows, do-

• Open Command Prompt as an administrator.
• Type inconfig/flushdns and press Enter.

• Restart your browser and try accessing the website again.

Fix Redirect Loops

Redirect loops can cause the size of cookies or headers to grow too large.In order to fix this error, you should check redirect rules in which you need to ensure that your site doesn't have a loop. As in the example states above, if Page A redirects to Page B and Page B redirects back to Page A, you need to fix redirects to prevent looping.

Use Local Storage or Session Storage

Local Storage and Session Storge can store data without adding it to request headers or cookies. In order to use local storage or session storage to fix the error, you need to switch to local storage or session storage, it is for the data that doesn't need to be sent with every request.

Contact the Site Owner to Report the Error

To Contact the site owner to report the error you have to locate contact information by looking for a "Contact us" page or support email on the website. When contacting the site owner or support team do add : A description of the error message. The steps you have already taken to try and resolve the issue. and any relevant screenshots or error codes. You can ask for their assistance in investigating and resolving the issue.

Conclusion

When you see 400 bad request error , it usually means that your browser is sending to much data to the server, either through cookies or through headers. To fix this issue, you can take some simple steps like cleaning cookies, reducing cookie size, etc. In essence, keeping things light and clean- whether it is the cookies which your browser stores or the headers- you can prevent the errors. You need to understand the causes and apply straightforward solutions.