Gmail Error 400: How to Fix It?

Jenny Lowrence | January 15th, 2026 | Data Backup

Are you getting Gmail error 400 when you try to sign in or access your inbox? It can be frustrating if you need to send or read important emails. In this post, we will explain what error 400 in Gmail is, its causes, and effective ways to fix it.

What is Gmail 400 Error?

Gmail error 400  is an HTTP code that prevents Gmail from loading properly. It appears in various forms such as “400. That’s an error”, “Bad Request – Error 400”, “Gmail error 400 invalid_request”, and “Your client has issued a malformed or illegal request”. It may occur when users are trying to log in, opening their inbox, or sending emails.

What Causes of Error 400 Gmail?

Here are some reasons for Gmail Error 400:

  • Corrupted Browser Cache & Cookies: If the cache is corrupted or outdated, then Gmail may fail to process requests properly, as a result in Error 400.
  • Outdated Web Browser: Older browser versions may not support Gmail’s latest features, which can cause compatibility issues, leading to this error.
  • Browser Extensions: Sometimes, browser extensions may conflict with Gmail functionality and cause this error.
  • Network Issues: An unstable internet connection can prevent proper communication with Gmail servers, causing malformed requests.
  • DNS Issues: Sometimes, Gmail 400 error may occur due to a Domain Name System issue and prevent your system from correctly resolving Google’s server addresses.
  • Malformed URL: An incorrect URL can send invalid requests, causing an error 400.

How to Fix Gmail Error 400?

Here are some methods that help to resolve error 400 in Gmail:

1. Clear Browser Cache & Cookies

A corrupted browser cache can cause many issues.

  1. Open browser Settings.
  2. Click on Privacy and Security >> Delete Browsing Data.
  3. Choose Cookies and other site data, and Cached images and files.
  4. Next, click Clear Data.

2. Disable Browser Extensions

Extensions may interfere with Gmail functionality. So disable them to solve error 400.

  1. Go to Settings, click on Extensions and Add-ons.
  2. Remove all the unnecessary extensions and restart your browser.

3. Update Your Browser

Outdated browser versions may not support Gmail features. As a result, Gmail error 400 invalid_request can occur. Ensure that you are using the latest version of your browser.

4. Try a Different Browser

Open your Gmail in a different browser or Incognito Window to check if it’s a browser issue or not.

5. Check Internet Connection

An unstable internet connection may cause of various issues like Gmail 400 error. Make sure your internet connection is stable or not.

6. Restart Your Device

Sometimes a simple restart can solve many problems. It can clear out any temporary issues that can cause the error.

7. Check the Gmail URL

Ensure you are using the correct Gmail address.

8. Sign Out and Sign Back into Your Gmail Account

Session-related issues can cause error 400. Sign out of your Gmail account from all devices and sign in again.

Bonus Tips: Backup Gmail Emails

If you are facing Gmail error 400 frequently, it may lead to account restrictions. To avoid this situation, you must take a backup of your Gmail emails. Advik Gmail Backup Tool is one such tool that will help you to save Gmail emails to your system in various formats. The software has various features such as bulk or selective backup, preserving folder structure, etc. Once you save emails offline, you can access them in any uncertain situation.

Conclusion

It can be frustrating when you get 400 error while opening Gmail. It is usually caused by browser or session-related issues. While this error can be fixed easily if you have the right solutions. In this post, we have discussed some possible solutions to resolve Gmail error 400.