It's possible DuckDuckGo is not installed. Try looking for it here; https://mycroftproject.com/

Fred,

Thanks, but this didn't help. I have installed DukDuckGo Privacy Essentials and I can access their serch engine, but it doesn't show up in the list of search engines Under Tools -> Search -> Default Search Engine.

Cheryl

Hi Cheryl, further down the search panel, there should be a box under the heading "Search Shortcuts". DuckDuckGo usually is listed in this box because it is one of the built-in options. If DuckDuckGo is not listed, could you scroll down below the box and click the "Restore Default Search Engines" button and see whether that brings it back.

You can check the "Help -> More Troubleshooting Information" (about:support) page to see what search engines are available.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

If everything fails then try to rename/remove search.json.mozlz4 in the Firefox profile folder with Firefox closed to rebuild the search engines registry.

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Firefox will rebuild search.json.mozlz4 from the built-in search engines.