Use a different search engine in Firefox Private mode

Firefox now* offers a native option to choose a separate search engine for private browsing.

To enable this open about:config, choose "Accept the Risk and Continue" if needed. Then set the private search options as follows(search for "search*private" to make it easier):

• browser.search.separatePrivateDefault = true
• browser.search.separatePrivateDefault.ui.enabled = true
• browser.search.suggest.enabled.private = true

Then go to Options> Search> "Choose a different default search engine for Private Windows only" and select the search engine of your choice in the drop down menu.

After that's complete, private browsing windows will use the private search engine by default. Also, if you choose the "Add search bar in toolbar" in options, the normal default will still be available under the "This time, search with:" option.

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*_{Tested with Firefox 73.0, but the feature may be available as early as version 71.0}

I thought this sounded familiar, and your link was the question I remembered. :-) It's the same with Firefox, there isn't a built-in feature that supports this directly. However, there are a few potential workarounds.

• One is the approach I suggested on the linked question. Create a shortcut that opens a private mode window and selects the private mode default search engine. That would change the setting for normal mode as well, so you could use another shortcut that sets the default back to the normal mode one and then closes the private window.

• Use separate profiles for normal and private browsing. In each profile, set the default search engine for that mode. You can keep both browser instances open at the same time if each uses a different profile, so switching would be just clicking on a different window.

  But if you don't need both open concurrently, you can set up a way to quickly switch modes. Type about:profiles in the URL window and it will take you to a dashboard page for doing stuff with different profiles. Right-click that tab and select Pin Tab. This will stick a mini-tab on the left end of the tabs bar for that page. When you want to work in the other mode, click that mini-tab and select the other profile--two clicks to change modes.