Firefox 71: set a custom private browsing search engine

Martin Brinkmann
Oct 5, 2019

Mozilla plans to integrate a new search-related feature in Firefox 71 that gives users options to set a custom search engine for private browsing.

Private browsing is a special browsing mode designed to improve local privacy for the most part; some data that is stored by the browser automatically in regular mode is not stored in that mode. Firefox won't remember visited pages or searches of private browsing sessions. Private Browsing mode has some tweaks in place that reduce the ability of remote sites to track users, Referer Path Stripping being one.

Mozilla thought about creating a super private browsing mode in 2019 but it is unclear if it will ever be designed and implemented.

Tip: you can open select sites automatically in Firefox's private browsing mode.

Firefox 71: custom private browsing search engine

The current stable version of Firefox, Firefox 69.x, uses the same search engine for regular browsing and private browsing. Firefox does support options to switch to a different search engine quickly using on-off searches but that would require direct user interaction.

Mozilla plans to add an option to Firefox 71 that gives users control over the search engine in private browsing mode. Firefox users who don't want to use the default search engine can set a different search engine for private browsing mode that way.

The feature landed in recent versions of Firefox Nightly, the cutting edge development version of Firefox, already. It is hidden behind a flag currently but that flag is only required until Mozilla enables the feature directly in Firefox.

How to set a custom private browsing search engine in Firefox

firefox private browsing search engine

  1. Open about:preferences#search in the browser's address bar; this should load the search settings of the browser right away. You can also click on Menu > Options and select Search when the page options to go there.
  2. Locate the "default search engine" section on the Search page.
  3. Uncheck the "use this search engine in Private Windows" option.
  4. Set a different search engine in the menu that is displayed.

Firefox will use that search engine from that moment on when you run searches in private browsing mode.

Enable the feature in Nightly

Here is what you need to do currently:

  1. Load about:config in the Firefox address bar.
  2. Confirm that you will be careful if the warning is displayed.
  3. Search for
  4. Set the preference to True.

The option to set a custom search engine for private browsing mode becomes available in Settings immediately.

Closing Words

Not all Firefox users may find the new option useful; those who have set the search engine to one run by a company that promises privacy protection may have little use for that feature, at least when privacy is concerned.

Those who have set it to Google, Bing or another major search engine may benefit from it when they use private browsing.

The custom search engine may also be useful if you want to separate searches, e.g. make all private browsing searches from a different search engine.

Firefox 71 will be released on December 3, 2019 according to the Firefox release schedule.

Now you: What is your take, how useful is the new feature? (via Sören Hentzschel)

Firefox 71: set a custom private browsing search engine
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Firefox 71: set a custom private browsing search engine
Mozilla plans to integrate a new search-related feature in Firefox 71 that gives users options to set a custom search engine for private browsing.
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  1. Ali said on April 5, 2021 at 11:23 pm

    Thanks man! I really needed this feature. I have to use google in my usual search but when I go private, I prefer to use DuckDuckGo.

  2. said on February 26, 2020 at 7:43 pm

    That s all good but the ISP still has your Loc and Internet address. Why not offer a VPN CAPABILITY like OPERA does? More Intl users may use Firefox if there was a way to totally remain private location wise. Loc privacy can be equally important.

  3. Johann Josef Wenzel Anton Franz Karl Graf Radetzky von Radetz said on October 7, 2019 at 9:19 pm

    Most user’s choices about search engines and bookmarks just leave me stumbling… Just create a simple homepage with your favourite search engines and most used sites and you’re set.

    Delete bookmarks inside browser and remove search tab.

    No bloat allowed !!

  4. ScrewKeyloggers said on October 6, 2019 at 2:07 pm

    In regards to the ‘Referer Path Stripping’ link, one should keep in mind that a URL and an HTTP referer [sic] header are not the same; and the latter is not added to HTTPS requests by specification.

    In regards to Web browsers’ address bar search, just disable this keylogger (that’s what it really is) and browse the search site of your choice instead.

  5. Jonas said on October 5, 2019 at 9:22 pm

    I’m not sure whether your pessimistic view (that there’s no privacy whatever online) is true or not… but my sense is that most people who use tools like ad-blockers and anti-trackers do so mostly to avoid annoyances, not to avoid being sent to a gulag. In Western-style countries, anyway.

    IMHO, the best way to restore some semblance of privacy would be to totally outlaw the private-data brokering business. Unfortunately, here in the US, corporations have most of the power — so that’s unfortunately not going to happen. Do the (better) EU privacy laws permit those evil panopticon brokers to exist?

  6. VioletMoon said on October 5, 2019 at 6:05 pm

    Oxymoron – Internet/privacy.

    The fallacy in the article and in responses is the notion that there is some way to remain anonymous on the Internet–disable ads, use ping blockers, use a VPN, use some “super private browsing mode with an ultimate privacy protecting search engine,” etc.

    Nope, one can’t even become a “little more private.” Once a connection is made to the Internet, all privacy and terms of agreement promising such privacy, are null and void.

    Your email, your voter registration, your mobile phone, your address, your purchasing habits, the encrypted messages sent to your mother, your banking transactions, age, sexual preference, gender, current employment, past employment, etc.–it’s all online.

    Regardless of whether one knows how to retrieve all past or present Internet activity or not; regardless of one’s delusional belief that there is such a thing as “private mode”; or regardless of how many times one erases tracks, clears histories, and/or deletes accounts from the past;


    surreptitiously, “anonymous” is being “watched,” “studied,” “placed in a database,” “analyzed by choices made on links,” “included in sets and subsets of users,” and identified and easily located to within several millimeters on a map that can be targeted and vaporized or brought in for questioning, sent to Guantanamo, or sent some anthrax.

    1. NSA said on October 6, 2019 at 8:14 pm

      Now that you posted this comment, @VioletMoon, we know _everything_ about you ;-\

  7. Anonymous said on October 5, 2019 at 3:45 pm

    This is sending the mixed message that people should switch to a more private search engine than the privacy hostile default one that pays them, but that it’s good enough if users do it only in private browsing mode, instead of for all use. (The private browsing mode that disables adblockers by default just like in Google Chrome to send its own fallacious message that extensions are statistically a larger threat to privacy when on than when off). And apparently, Mozilla won’t even go as far as actually changing themselves the default search engine in private browsing to a more private one ! I remember reading one of their employees pleading as a last resort for a web tracking feature they had implemented in Firefox, “But what if our users want to be tracked ?”.

    It reminds me of those users who won’t install ublock origin just because the deliberately inferior default Firefox content blocker exists. Instead of fully doing what’s best for the users, providing deliberately insufficient protection mechanisms with the consequence of inciting users not to seek one that is optimal for their own interests.

    Mozilla, always one foot on each side of the frontline. And that’s still a generous interpretation of their actions.

  8. Anonymous said on October 5, 2019 at 11:35 am

    Thank you for news Martin. I think Firefox graphical settings are too complex. Now I have to scroll down even if I have bigger monitor. About:config settings are good thing but after every update there is more choices. Options that are obsolete. They can also conflict or can be redundant with extensions.

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