How to Fix Gmail 400 Error? Step By Step Guide for Bad Request Error

“How to fix Gmail error 400?”. Many Gmail users often ask this query. It can be frustrating when you try to log into your Gmail or connect a third-party app like Thunderbird or maybe Outlook, only to see “Gmail 400 Error.” When encountered over and over again, the 400 error drains both time and efficiency.

Google 400: That’s an Error, also known as “Authorization Error,” or “400 Bad Request,” is an HTTP status code. This occurs when the server is not able to understand the request and fails to execute.

Consider it like when you walk into a Coffee shop and ask for “Cappuchoco-frappo,” the host will not be able to process it. Similarly, when you enter a broken, unclear, or malformed your browser or an app is not able to process it, and you see a Gmail 400 error. This ultimately blocks you from sending or receiving emails.

This error can be found in multiple variants, too, like 400 invalid_request, admin_policy_enforced, and redirect_uri_mismatch.
This guide is a one-stop solution for why you are facing this error and how you can resolve it, no matter if you’re on iPhone, Mac, Firefox, Thunderbird, or integrating via the Gmail API.

Common Causes of Error 400 Gmail

A Gmail 400 error is mostly a client-side issue. It means the input sent from your end, in most cases, is malformed. Here is a detailed breakdown of the “Bad Request” error:

• Malformed URL: The web address format or syntax can be missing the protocol or port. There may be invalid characters in the URL.
• Network Issue: Internet connection is unstable; thus, requests sent from your end may be incomplete or not sent at all.
• Outdated or Corrupted Cache/Cookies: An outdated or too large cache can cause conflict with Gmail’s Server, causing the Error 400 Gmail.
• Browser Extensions: Ad blockers and script modifiers extensions can alter HTTP requests, leading to server-side rejection.
• Google Account Sync Issues: When accounts are not synced across devices and platforms like Contacts, Calendar, etc, the bad request error could be triggered.
• DNS Issues: The server failed to convert and access the URL into an IP address due to a network or hardware-related error.
• Gmail 400 Error iPhone: As per Google’s new security update, older or outdated iOS or macOS versions do not meet the security protocol, resulting in syncing issues.
• Safari on Mac: Safari has a content blocker that sometimes even restricts authentication pop-ups from Google, leading to a 400 error.
• Admin Policy: Gmail error 400 admin_policy_enforced occurs when, for security reasons, the third-party administrator prevents the Google Workspace data.

There can be several other API & OAuth-related errors, while in some cases, a VPN or proxy server also interferes with the server. Now that you have a good look at the common reasons, let us learn how to fix 400 unauthorized error.

Learn To: Fix Gmail Something Went Wrong Error

Quick Fix- How do I fix error 400 Gmail?

Note: OAuth is a feature that allows any other third-party app to access the information stored in Google’s database.

Troubleshooting Steps to Fix Gmail 400 Error

Follow these steps and methods to resolve the problem:

Fix Browser & Client-Side Issues

Since the error is most likely on the client side. Solving the browser and client-side issues is most likely to resolve the issues.

1. Check the URL: Ensure that the URL is correct. It must contain all the protocols, and there must be no missing or invalid characters or ports. Simply refresh and retype.
2. Clear Browser Cache & Cookies: Outdated cookies that have been there for a prolonged period are most likely to get corrupted.
   • Chrome: Open the Browser. Click on the “More”(three dots) >> “Delete browsing data”. Make sure you check all the boxes. Click “Delete Data”.
   • Firefox: Open the Browser >> Settings. Under Privacy & Security. Go to “Cookies and Site Data,” then press “Clear.”
   • Safari: Open Safari on Mac or iPhone. Go to “Preferences” >> Privacy. Under “Manage Website Data,” press Remove all.
3. Disable Browser Extensions: Disable all the browser extensions. Relaunch to resolve Gmail 400 error.

Device or Browser Related Fixes

1. Try a Different Browser or Incognito Mode: Check on multiple browsers like Chrome, Firefox, or Edge.
2. Restart Your Computer: It clears temporary glitches affecting browser performance.
3. Mac/Safari Specific Fixes:
   • Disable Content Blockers: Specifically for Google. Click on the […] more button. Disable the content blocker.
   • Allow pop-ups: Go to “Safari” >> Preferences under “Websites” >> Select “Pop-up Windows” and allow for Google.
4. Remove and Re-add Account: If there are some issues caused due to account information corruption in a particular device.

Fix Network & Security Conflicts

1. Check Your Internet Connection: A stable internet connection is needed to properly communicate with the server. Switch between the WiFi and the Mobile Internet Connection. It will help resolve the Gmail 400 error.
2. Disable VPN/Proxy
3. Disable Antivirus: In some cases, antivirus software can hinder security protocols. Click on “Start” >> Windows Security. Under “Virus & threat protection,” click on “Manage Settings”. Turn off “Real-time protection” and press Yes. After a while, turn the VPN back on if needed.
4. Clear DNS Cache: Clearing the DNS cache will help connect to the latest version of the website. Open CMD Prompt >>
   Type ipconfig /flushdns and “Enter.” Turn your computer off and on again.

Fix OAuth, API & App Integration Errors

There can be several issues that can be resolved with the Google OAuth settings. Let us have a look at them one at a time. These methods are specifically for developers and third-party app users.

1. Gmail Error 400 redirect_uri_mismatch: Locate the correct URI. Open your Google Cloud Console. On the left-hand menu, go to APIs & Services and then OAuth consent screen. Under the “Credentials” section >> Authorized redirect URIs. Click Save.
2. Contact the Third-Party Developer: In case of Gmail error 400 admin_policy_enforced, which you face while “Sign In with Google,” you can contact the developer.
3. Thunderbird Gmail 400 Error:
   • Here, ensure that the IMAP/SMTP settings are properly configured.
   • Open “Thunderbird“. Go to “Tools“, under Account Settings, choose the account you are facing issues with. Under the Authentication Method, choose OAuth2. Finally, save changes.

To simply resolve these issues, you can wait and try again in a while. In most cases, the Gmail 400 error is temporary.

Pro Tips to Prevent Gmail 400 Errors in the Future

The above troubleshooting steps must have helped you resolve Gmail error 400. Let us look at some tips to ensure you do not encounter this issue over and over again.

• Do not Bookmark expired Gmail links.
• Update your browser and Gmail application frequently.
• Make sure you regularly clear cache and cookies.
• Connect with the IT team instantly when encountering such issues.

What to Do If Gmail 400 Error Appears Repeatedly?

If you encounter an authorization error 400 or a “Bad Request” error, it hinders your efficiency, and you can not access your important emails. Multiple such errors can indicate Gmail of suspicious activities. This may lead to temporary or permanent account restriction. To avoid this scenario, you need to safeguard your Gmail information. Try our Email Backup Solution.

This robust tool allows saving Gmail information securely, in multiple formats, instantly. So you never lose access to Gmail email information. It also gives you the flexibility to access them even offline, all while maintaining the same folder structure, look, and feel.

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Conclusion

We understand that Gmail Error 400 is easy to resolve, but it can be disruptive and risky for your Gmail information. In most cases, it can be easily resolved by clearing the browser cache or simply disabling the VPN or antivirus software. In other cases, several in-depth steps and troubleshooting actions have to be taken. Don’t worry, this guide includes a solution to the Gmail 400 error, whether encountered in iPhone, Mac, or platforms like Firefox or Thunderbird. Even after trying the steps, if you find that you are facing the issue, contact Google support. To ensure you have complete control over your Gmail, use our advanced tool to safeguard and have offline access.