Manually Delete MIT Personal Certificates in Firefox

WARNING: If you have used S/MIME for email encryption, you should export certificates, in order to retain a backup copy, before deleting them from the browser. How can I tell if I've used S/MIME for email encryption?

1. Open Firefox Preferences
   1. Click on the three bars in the upper right and select Preferences from the menu.
      
      
   2. Open Preferences from menu path:
      • On Windows (depending on your version of Windows and Firefox):
      • Tools > Options > Preferences
      • Firefox > Options > Preferences
      • Options (next to the gear icon) > Preferences
      • Tools > Options > Advanced > Encryption (skip to step 3)
      • On Linux: Edit > Preferences
      • On Mac OS X: Firefox > Preferences
        
        
2. Select the Privacy & Security pane. Then scroll down to the Certificates section.
   
3. From Your Certificates, click View Certificates.
   
4. Select the expired or duplicate certificate and click the Delete button. You will be prompted if you want to delete the certificate. Click OK to continue.
   
5. Close and re-open Firefox, and confirm that you have one, non-expired certificate.

Note: You also want to empty your browser cache after deleting your certificate.

See Also

• Certificates Landing Page