Firefox Search Engine Cautions, Recommendations

Firefox Search Engine Monetization

See the revision history at the end of this document.

When 'free' software isn't

I suggest reading The Mozilla Monster as a primer.

Have you ever wondered how Mozilla gets paid by the privacy-hating mega-monopolies like Google? Simple; when you use the default search engine plugins that are packaged with the browser, parameters similar to these are added to your search query:

name="appid" value="ff"
name="hspart" value="mozilla"

These parameters inform the search engine that you're using a Firefox/Mozilla product and that's all it takes for Mozilla to rake in the dough. If you do not wish to support highly unethical companies like Google, and/or value your privacy, read on...

Types of search engines

The two primary types of search engines are meta search engines and search indexes and it is important to understand the difference. Google, Yahoo and Bing for example, use software robots called "crawlers" to discover and index web content. In other words these companies actively seek out updated and fresh content to store in their databases so it's ready for you to find. On the other hand, meta search engines do not index the web and instead rely upon third parties like the aforementioned to provide their search results. When you use these so-called "alternative" search engines, such as DuckDuckGo, Startpage, Searx, etc., you are still subject to the filter bubbles and censorship that is employed by the corporate giants like Google. That said, the privacy-respecting meta search engines still make a great deal of sense since they offer a method to access the data-harvesting corporate giants without the privacy violations that accessing them directly would incur. Understand though that they are not true alternatives as they are often described, but rather proxies. These alternative search engines are also subject to local laws, such as secret surveillance requests issued by a government.

Indexing the web and storing the massive amount of data that results is an incredibly expensive proposition which requires a massive amount of infrastructure and this is why the much smaller meta search companies like DuckDuckGo, Startpage, Qwant and others rely heavily upon corporations like Alphabet's Google and Microsoft's Bing. There are better alternatives that both respect your privacy and are censorship resistant however. Ever hear of a peer-to-peer distributed search engine? Imagine a free, open-source, decentralized search engine where the web index is created and distributed by ordinary people using personal computers, each storing a piece of the whole. This is what the developers behind YaCy have done with their search engine and i think it's a great way to escape the filter bubbles created by big tech.

For a list of alternative search engines, see Alternative Search Engines That Respect Your Privacy.

Adding search engines to Firefox

Possibly the easiest way to mitigate risks to your anonymity posed by the default Firefox search engines is to simply disable all of them and use alternatives such as the open source and highly customizable Searx meta search engine which you can host on your own server if you like, or you can use any one of a number of Searx instances hosted by others. Like DuckDuckGo, Startpage and others, Searx does not use robots to crawl the web and index content like Google, however the big difference between Searx and most of the other meta search engines is that it is capable of pulling results from many other indexes including Google, Yahoo, Bing, Wikipedia, DuckDuckGo, Startpage, Qwant and more, as well as decentralized peer-to-peer indexes such as YaCy. The Searx interface also offers a lot of configuration options for fine-tuning your search results, including the ability to select exactly what combinations of search engines you want to use for a particular type of search, of which there are currently 10.

One easy way to add Searx to Firefox is to locate a hosted instance which you like and which is preferably close to you geographically. After loading the search page, open the search bar menu or the address bar 3-dot menu and click the "Add" menu item. A potential pitfall with the third party Searx instances is that the server may be logging traffic, such as IP addresses, location, etc., so you'll have to decide whether you can trust them.

Most other search engines can be added to Firefox in the same way, but there are additional methods also. The Mycroft Project hosts tens of thousands of preconfigured search engine plugins for a variety of web browsers, the top 100 of which are listed here. They also have a form for writing your own search plugins. Although it is not possible to review the code from the main listing of search plugins, you can use their submission form to do so by mousing over the plugin name to reveal its numeric ID, then filling in that ID in their submission form page. Because Mozilla changed they way search engine plugins are added to Firefox, you'll need the Add Search Engine from Mycroft Project add-on to install the search plugins from Mycroft.

Another easy way to add a custom search engine to Firefox is with the Search Engines Helper add-on by Soufiane Sakhi which allows more control over the above methods, including the ability to define the website icon path or base64 code (a binary-to-text encoding scheme that encodes the site icon in text form). The advantage of using a base64 encoded version of the site icon is that the browser won't have to fetch the icon from the server. A great on-line resource for converting an icon to base64 code is the Base64 Encoder utility which can accept the icon URL or an uploaded file.

You can also use the mozlz4-edit Firefox add-on by 'serj_kzv' to add and edit the Firefox search engines. This slick extension allows you to edit the search.json.mozlz4 search plugin file directly from within Firefox, though a browser restart is necessary before the changes are realized. It is in this file that Firefox stores the code for all of the search engine plugins. If you use this tool, be careful not to touch the default search engines that are packaged with Firefox, else all your changes will be lost. Instead you can create copies of the default engines and sanitize the copies. Read on...

Manually editing search.json.mozlz4

If you would rather avoid the hassle of manually editing the default Firefox search engine plugins, see the Pre-sanitized search plugins section below.

If you choose to use the default search engine plugins provided by Mozilla, you may want to sanitize them in order to help protect your privacy, however you should be aware that doing so will not prevent tracking or other privacy risks when using the default search engine plugins, especially if you have JavaScript enabled. If you insist on using the default search engines, you should use something like the ClearURLs add-on which at least strips the tracking parameters from the search engine result links. You should also disable JavaScript for the search engine web page if possible. For this i would recommend something like uBlock Origin by Raymond Hill.

If you have already added custom search engines to Firefox, then the first thing to do before you start hacking is to create a copy of search.json.mozlz4 and work with the copy, reason being that if you mess up, Firefox will will delete all of your search plugins and restore only the default ones. If you don't want to see or use the default ones, disable them in the search preferences of Firefox rather than removing them from the plugin file.

To edit the search.json.mozlz4 file you first need to decompress it. There's at least a few utilities available that will handle this, but i would suggest using the mozlz4-edit Firefox add-on by 'serj_kzv' since it is very easy to use and it provides a basic code editor with syntax highlighting. If you use this tool to modify the default search engine plugins that are packaged with Firefox, you must make copies of them and edit the copies, else Firefox will rebuild the entire file and all your changes will be lost. Also be sure to give the new entries a different name since no two plugins can share the same name.

Download pre-sanitized search plugins

If you do not want to sanitize the default search engine plugins yourself you can download my pre-sanitized copy which contains a search.json.mozlz4 file that should work for Firefox version 57 and up ("up" meaning until the next time Mozilla decides to break everything again). The download contains the default engines which come with U.S. English version of Firefox 62, plus the sanitized versions of them, plus all of the engines i personally use. All in all there's over 40 search engine plugins which you can edit or disable as you see fit. Many are already disabled since i only use them occasionally, so be sure to adjust as necessary in your Firefox Search preferences.


Install: Backup your existing search.json.mozlz4 file, then extract the the one from the archive to your Firefox profile directory and restart Firefox.

Removing Firefox system add-ons

Mozilla packages some system add-ons with Firefox, installs them without your permission and doesn't provide the user with any convenient means to remove or disable them. These system add-ons have been used for very controversial purposes in the past. To remove them, see the 'System add-ons' section of the Firefox Configuration Guide for Privacy Freaks and Performance Buffs.

We've only scratched the surface...

Sanitizing the default Firefox search engine plugins is a good start, but there is much more to do if you're interested in circumventing the risks to your privacy. For further information see the Tech section of this website.


Special mention goes to 'Thorin-Oakenpants' (aka 'Pants') as well as the 'arkenfox' crew and their GitHub repository where they host an excellent privacy-centric user.js for Firefox and its derivatives, as well as an extensive Wiki full of valuable information.

Resources at

External resources:

Revision history

Click to expand...


  • first publish


  • added this change log
  • corrected an error in the pre-sanitized Wikipedia search plugin and re-uploaded
  • added information as suggested by 'Pants' in his comment below, particularly details and resources regarding the system add-on in a new section titled "Removing the 'Follow On Search' system add-on"
  • added Hulbee and MetaGer to the search engine list
  • added a "Decentralized" column to the search engine table
  • added resource: 5 Best Search Engines That Respect Your Privacy -
  • misc. cleanup and edits


  • corrected typo in metager URL
  • added "Requires JS / Cookies" column in search engine table
  • changed links for search engines in table to point to company/about page and added links to point to search page
  • added link to the 'lite' version of DDG
  • added a link to the uBO filters to block Startpage/Ixquick tracking images
  • misc. minor edits


  • added "Client Required" column to search engine table
  • corrected some info regarding the search engines in the table
  • minor misc. edits


  • added a link to the Duck Duck Go: Illusion of Privacy article
  • added findx to the search engine list
  • minor edits


  • added Qwant to the search engine table


  • misc. edits and added info, nothing really important


  • very minor edits


  • moved the list of alternative search engines to it own page
  • minor edits


  • minor change to the section 'Sanitizing the default search engine plugins' thanks to commenter 'nohamelin' - more changes coming shortly thanks to this persons comments


  • updated search plugin import/export instructions as per the very helpful comment left by 'nohamelin', the developer of the XML Search Engines Exporter/Importer add-on in which he made available Scratchpad scripts that work with FF v57+
  • corrected an error in the pre-sanitized search engine archive, added Startpage and re-uploaded a new archive
  • misc. minor edits


  • polishing


  • major changes, additions and deletions


  • fixed corrupted download files
  • added info about Add custom search engine add-on
  • added better instructions for installing the search plugin file, search.json.mozlz4
  • minor edits


  • rewrote the section on manually sanitizing search plugins
  • various minor edits


  • updated the search.json.mozlz4 file
  • spelling corrections


  • updated the search.json.mozlz4 file
  • minor edits


  • referred to my Firefox configuration guide for info on removing system add-ons


  • moved info about Mozilla to it's own page
  • minor edits, corrections


  • updated search.json.mozlz4
  • minor edits


  • many changes - much was rewritten and some parts were removed
  • i removed the bulk of the instructions for editing the search.json.mozlz4 since it was obsolete - thanks to 'Damien' for contacting me about an issue with this article which reminded me that changes were needed

Email me when this content is updated.

Firefox Search Engine Cautions, Recommendations

29 thoughts on “Firefox Search Engine Cautions, Recommendations”

  1. Hello,
    “Sanitizing the prefs.js search engine preferences

    Another item you should check is whether prefs.js in your Firefox profile directory contains any preferences. To sanitize these, load about:config in the browser address bar and enter in the search field. If none are found, great, but at the time i originally wrote this article there were two preferences found; and The default values may be different in your case, but in mine they were data:text/plain, and an empty string, respectively. What you should do is create a custom user.js file to store your modified preferences if you don’t already have one, then copy the following code to it:

    user_pref(“”, “”); // sanitize Yahoo
    user_pref(“”, “”); // sanitize Yahoo

    It doesn’t work, I still have (screenshot):

    Thank you.

    1. thanks for bringing this up because this article needs updating

      > It doesn’t work, I still have (screenshot):

      yes, the pref is there, but it has no value – in other words it’s not doing anything, however, it looks like these ‘’ prefs have been removed at some point – in your screen cap you have a garbage can icon on the right – click that for both of the ‘’ prefs and they will be deleted

  2. Hi
    regarding default search engines : I only checked off duckduckgo. However when I enter about:support, I notice that ebay appears as a default search engine classified as true just like the rest. it seems strange as it doesn’t appear as an option in preferences ( 80.0, ubuntu 18.04)

    1. hello back
      i’m not sure what the reasoning is here, but apparently ‘disabling’ the search plugin really means ‘hide it from the UI’, not disable … you know, kinda like Macro$haft did with IE; you could hide its icons, but you couldn’t remove the damned thing

  3. Sweet! I do find that using DuckDuckGo lite is just too much of an inconvenience for me though, no image search and such. Also is there a way to make firefox highlight the searchbar instead of address bar on startup and new tabs?

        1. i wouldn’t advise that others do this without being aware of the very real risk to privacy – everything you enter in the address bar will be sent to the search engine

          also, just in case you don’t already know, if by chance you’ve edited the ‘arkenfox’ user.js directly, that’s a mistake that will cost you when there’s an update which will overwrite all your changes – instead, add your changes to a user-overrides.js file and use the ‘arkenfox’ updater script to update the user.js and append user-overrides to it

          for those that are wiling to risk their privacy for whatever reason, the pref is “ keyword.enabled

          1. I noticed a few more things I didn’t see before, search engines below the location bar for the one-click search also no longer work and dns over https and disabling restore previous session don’t retain settings on restart. I managed to get the searches back beneath the location bar with the setting “browser.urlbar.oneOffSearches” and got dns over https with both “network.trr.mode” (1 for cloudflare, 2 for custom) and “network.trr.uri” & “network.trr.custom_uri” (url for custom provider). Still haven’t figured out what the deal is with the restore session on start always being on.

            1. if i understand you correctly, you do not want to restore the previous session on restart – if that’s the case, look at “”

              here’s a handy trick if you’re trying to figure out which preference is tied to a setting in the Firefox preferences UI –
              either use a text/code editor that can monitor file changes and then display the difference, or a ‘diff’ program – in the case of the latter, create a copy of prefs.js, then change the setting in Firefox, then ‘diff’ the 2 prefs files

              1. You know I discovered Thunderbird has it’s own search.json.mozlz4, not sure how relevant it is to security though.
                Also I’ve found some use from the following search engines in addition to the ones you provided:
                Google Translate
                Invidious (multiple hosts)
                Nitter (multiple hosts)
                PCGamingWiki (only useful if you play video games like me)
                Yandex translate

                1. for the purpose of security/privacy i treat Thunderbird strictly as an email client, not a web browser – i kind of wish the developers would also

                  i appreciate suggestions, but as for the other engines you list i want to stick to general search engines – if i started listing specialized engines i might spend the rest of my life on this one page :)

                  off-topic, but on a political/privacy note, i would discourage anyone from buying anything from Amazon

  4. Thanks for the useful article;
    how can we detect to which servers/IPs Firefox is sending our information to? so we can block that specific address in windows host file…

    1. if you mean with regard to search engines, you don’t have to – just use alternatives to the default search plugins that ship with Firefox

      if you’re worried about other stuff being sent, i’m not knowledgeable enough to know for certain what Firefox is sending where – you’d have to do your own research – also there are very legitimate reasons for Firefox to be calling home, such as grabbing lists of malicious add-ons, websites, security stuff, etc., so if you block anything, be careful what you block – that said, one of my guides might be of use – another thing you can do is search prefs.js (about:config) for ‘http’

  5. I realize that this page is somewhat dated, but Linux Mint limits default installed search addons in Firefox to those who have supported their distro’s development, but grudgingly gives a link to a somewhat larger set. I tried to use Scratchpad to install the sanitized search engines downloaded from the included link, but Scratchpad looks for HTML files and doesn’t recognize the sanitized search addons, even if the zip file is unpacked. Maybe I am doing something wrong, but I followed the instructions to the letter, and tried several times. Maybe it doesn’t work in Linux?

    1. I realize that this page is somewhat dated

      actually i updated it today and yesterday

      you don’t have to install the search.json.mozlz4 file – just unpack the .zip and copy the file to your profile directory – if you downloaded the file yesterday, download it again – i changed them

      let me know if you have further problems and, in the mean time, i’ll update the guide with better instructions

  6. (XML Search Engines Exporter/Importer developer here)

    Nice text. I want to add that the list of search plugins included by default in Fx is highly dependent of the build installed: that given list is for the en-US build, I think, and it changes for other locales, according to regional deals done by Mozilla, between other things.

    Now, given that no WebExtensions add-ons interacting with your search engines can be written yet, that leaves us for Fx57+:

    * First, you can get easily the original XML opensearch definition of all the engines included by default navigating to the “resource://search-plugins/” uri. From here, you can inspect them and save them to disk for manual sanitizing.
    * I adapted from the add-on some scripts to import/export engines via Scratchpad; it’s a bit awkward to use, but it should help:

    Also, be aware that Firefox dropped recently the support for adding engines from the searchplugins/ folder after deleting search.jzon.mozlz4; it will aply since Fx58:

      1. I got the message, that it couldn’t be removed as the file/ filecatalog did not exist. english is not my first language, so i’ve translated the message. tech terms may not be correct. I’m no savvy myself, so I’m only familiar with the most common terminal commands. I do attend a local community. they might know about alternatives. yet, I’m the only one pro privacy. off subject: this is a great blog. very user friendly and in depth. thank you @pants for linking at arkenfox

  7. Excellent article 12bytes. Really well done mate :)

    Some items for thought:
    – users should note some engines will require stripping tracking of search *results* (eg utms on google)
    – Firefox has a system add-on called Follow On Search, you should kill that (see arkenfox user.js)
    – XML Search Engines Exporter/Importer is not Web Extension (yet?) so for FF57+ users, I guess we can use a portable legacy FF to create the file(s)?

    1. Also remember that in a lot of cases it is better in the first place to use a site specific search engine as well. For example, I have added an iTunes search engine so no-one but iTunes knows I search for Taylor Swift .. #GoTayTay :)

    2. thanks for your input Pants! much appreciated – i updated the article to address this stuff and added a section “Removing the ‘Follow On Search’ system add-on”

      Q: do you know how these system add-ons are loaded – are they loaded dynamically each time FF starts like other add-ons, or are they actually installed/cached some place? i’m wanting to be sure that deleting them is sufficient

      1. System add-ons are listed under about:support>”Firefox Features” – they act just like normal extensions AFAIK (except no disable/uninstall options). Delete the xpi and restart FF and you’re good to go.

        System add-ons are packaged with each Firefox application update (full updates at least). I use portable FF, so I am not sure about installed version behavior re dot releases. If I try to update and I have deleted some system add-on xpi files, the update fails and FF prompts for a full package instead (although the last update from 55.0->55.0.3 didn’t? Can’t remember! Dot releases may vary.). Anyway, I keep an eye on my system add-ons directory, and I only do updates now by downloading the packages (yes they include all the system add-ons too – both 32+64bit app/dirs)

        One of the reasons system add-ons exist, is so that patches/changes can be pushed without an app update. But the update check and update settings can have an effect. See: . The arkenfox user.js checks for app updates but lets you decide when to apply them – so until this bug is resolved, you won’t get system add-ons re-added or updated without your knowledge.

        You could also try 0505: “extensions.systemAddon.update.url” – if the system doesn’t know where to go, what can it do :) The only reason this is inactive in the js, is because this mechanism was initially designed to PUSH fixes – I think it was spurred on by a critical vulnerability in pdfjs a few years ago (Yes, pdfjs is a system add-on, but seems to be a special case compared to how/where it is stored)

        1. thanks for the clarification

          in my case, with Linux, no system add-ons were displayed in about:support and, actually, there wasn’t even a section called ‘Firefox Features’ – the ‘follow-on search’ add-on wasn’t present either, though others were

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