After Mozilla released Firefox Quantum which requires that add-on developers modify the source-code of their add-ons completely, many of the add-on developers gave up and never released any updates. For example, one of the very popular add-ons DownThemAll, a powerful download manager for Firefox, no longer works in the newer versions of Firefox. In fact, the developers of this add-on got so frustrated that they decided to quit all the development and let the domain name associated with this add-on expire (the domain name downthemall.net expired on 29th August 2018).
If you want to keep using the older versions of such extensions (as the older versions are still available from the Mozilla add-on repository), you have to switch over to Waterfox – a Firefox based browser that is not showing so much eagerness to update to the Quantum source code base. Usually when you install Waterfox in your PC, it asks if you want to import Firefox profile.
But if you miss this step or decide to import data from some other web browser, then you can manually import it later in the following manner:
- Launch Waterfox, type about:support in the address bar and press Enter.
- Find the Profile Folder setting and click no the Open Folder button next to it.
- The folder that opens will have a sub-folder with .default appended to the folder name. Keep this File Explorer window open.
- Close Waterfox browser.
- Repeat the steps 1 to 3 for Mozilla Firefox too. Keep this window open as well and close Firefox browser.
- Copy the contents of the folder opened in step 6 to that opened in step 3. If it asks you to overwrite the files, choose Yes and let it overwrite the files.
- Now you can launch Waterfox web browser and you will find that all the settings, extensions, bookmarks, passwords etc., have been imported from your Firefox profile to Waterfox.
If you have not installed Waterfox web browser and want to use it in order to use older versions of some add-ons that are no longer being updated, you can download it from https://www.waterfoxproject.org/.