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How to Fix 400 Bad Request Error in Microsoft My Apps
Question details
Users need to resolve a 400 Bad Request error that blocks access to applications via the Microsoft My Apps portal.
- Product
- Microsoft My Apps
- Device & OS
- not provided
- Scenario
- Attempting to launch an application directly from the Microsoft My Apps portal.
- Observed behavior
- The browser displays an nginx error page stating '400 Bad Request: Request Header or Cookie Too Large'.
Ensure you have your Microsoft 365 login credentials handy, as clearing your browser's cookies will log you out of your current sessions.
Clear Browser Cookies or Use a Private Window
Using an incognito window or clearing outdated cookies removes the oversized request headers causing the server error.
The 'Cookie Too Large' error typically occurs when your web browser accumulates too much cookie data for a specific domain, exceeding the nginx server's accepted size limit.
Launch a private or incognito browsing window. You can do this by pressing Ctrl+Shift+N in Google Chrome or Ctrl+Shift+P in Mozilla Firefox and Microsoft Edge.
Navigate to the Microsoft My Apps portal, log into your account, and attempt to open the application again to see if the error is bypassed.
If the application opens successfully in the private window, return to your main browser window. Go to your browser's privacy and security settings, search for Microsoft and Office domains, and clear their specific cookies and cached site data.
Contact Your IT Administrator
If the issue persists across different browsers and affects multiple users, it indicates a broader server-side configuration problem.
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Frequently Asked Questions
Why does the 'Request Header or Cookie Too Large' error occur in Microsoft My Apps?
This error happens when your browser accumulates too much cookie data for Microsoft websites over time. When you try to access My Apps, the browser sends all this data in the request header, which ends up exceeding the strict size limit configured on Microsoft's nginx servers.
Can I fix this error without losing my saved passwords?
Yes. By clearing only the cookies and site data for Microsoft-specific domains (such as microsoft.com or office.com) in your browser settings, rather than your entire browsing history, your saved passwords and active sessions for other websites will remain completely intact.
Is a 400 Bad Request error a sign of a virus or security breach?
No, a 400 Bad Request error is simply a communication mismatch between your web browser and the remote server. It indicates that the server cannot process the web request because the header is too large, not that your device is compromised or infected.
