As you know, to fix the problems such as slowness and other issues Firefox users face, Mozilla has introduced Reset feature from version 13 onwards, you can find a Reset button on the “Troubleshooting Information”/about:support page. This feature is also useful to remove malicious toolbars and restore search engine defaults, which is the most obvious reason for using this feature.
After resetting Firefox, you’ll find “old Firefox Data” folder on your desktop. Mozilla intention behind on adding this folder to the desktop after reset is to let you restore your old profile data if you didn’t find much help with reset. And more over, you can restore all lost customization including add-ons, without needing to install them again using this folder, but how is the question? We’re explaining that below with step by step in detail.
Restoring Firefox Old Profile Data after Reset
1. After Resetting Firefox, Exit Firefox browser.
2. Backup current Profile folder using tools like Firefox backup tool or MozBackup or you can manually copy Profile folder- click on “Show Folder” on Troubleshooting Information page- and paste to another location on the hard drive.
3. Open Old Firefox Data folder and copy all files in it with Ctrl +C button, now open Firefox profile folder (use the above mentioned method to reach there).
4. Use Ctrl+V to paste them, Windows Explorer shows “confirm folder replace” dialog, at the bottom of it select “Do this for all Current items” (check the screenshot below) and click “Yes” button.
5. Next “Copy File” dialog appears on screen with message “there is already a file with the same name in this location, select “Do this for next (number shown) conflicts“ at the bottom, and click on “copy and replace”.
That’s it! Your old Firefox profile data has been restored. Open Firefox and check to confirm that.