Firefox Privacy – The Complete How-To Guide

Mozilla Firefox is arguably the best browser available that combines strong privacy protection features, good security, active development, and regular updates. The newest version of Firefox is fast, light-weight, and packed full of great settings to protect your privacy.

It is for this reason that I consider Firefox to be the best all-around browser for privacy and security. It remains a solid alternative to some of the other options, such as Google Chrome, Microsoft Edge, and Safari.

Another great aspect of Firefox is that it is highly customizable, which is the point of this guide. Below we will go over how you can customize Firefox to give you the security and privacy you desire, while still working well for day-to-day browsing.

But before we jump in, let’s cover some important details.

Important considerations

There are many factors to consider when configuring Firefox to meet your needs, including your threat model and browsing preferences. In other words, there is no “one-size-fits-all” configuration that will work for everyone. This guide is a basic overview covering some of the different configurations options.

Before you start configuring Firefox and installing a bunch of add-ons, it’s important to consider browser fingerprinting.

Browser fingerprinting

The issue of browser fingerprinting (or device fingerprinting) is a big topic that covers all the different ways you can be tracked and identified by your system and various settings. All of the different add-ons you install and preference modifications you make to Firefox are inputs that can potentially be used to identify and track you.

Herein lies the catch-22: the more browser add-ons you install and settings you modify, the more unique you will be and thereby easier to track and identify.

And that leads us to the second point that…

More is not always better

When it comes to browser add-ons and modifications, you don’t want to be like that kid who puts every topping imaginable on his ice cream. More is not better with ice cream toppings or with Firefox browser add-ons.

Aside from the issue of browser fingerprinting, having too many add-ons may also slow down performance. Many of the popular Firefox add-ons also fulfill the same functions and are redundant when used together.

Therefore it is best to strike a balanced approach. Install and modify only what you think will be useful and necessary for your specific situation, and nothing more.

Proceed with caution

Modifying some of these settings may interfere with your browsing and break some websites (the website won’t load properly). Therefore taking an incremental approach may be the best way to proceed. You can continue to install add-ons and adjust your settings as you see what works with the websites you regularly visit.

This allows you to modify the settings, create exceptions, or add sites to a whitelist.

Firefox privacy settings

Before you get going with Firefox you may want to adjust the following settings for better privacy.

Note: if you are a Mac OS user, you will see the word “Preferences” in your menu rather than “Options” as it is listed below.

Disable telemetry

With the latest version of Firefox, it is configured to share “technical and interaction data” with Mozilla. This includes the ability to “install and run studies” on your computer. You can learn more about these studies and data collection practices if you want, but I’d recommend disabling these settings.

To disable go to Open Menu (three bars at the top right corner of the browser) > Options > Privacy & Security > Firefox Data Collection and Use and then uncheck the boxes as you see below:

firefox privacy telemetry

You can also disable data sharing with Firefox for Android by going to Menu > Settings > Privacy > Data Choices and then uncheck all three categories for Telemetry, Crash Reporter, and Mozilla Location Service.

Note: You can also disable this in the About:Config settings with toolkit.telemetry.enabled set to false.

Change default search engine

Firefox now uses Google as the default search engine. Since Google is recording your search queries to hit you with targeted ads, it’s a good idea to use an alternative to Google in the interest of privacy.

To do this, go to Menu > Search > Default Search Engine. Unfortunately, Firefox does not provide you with too many alternatives directly in the settings area. However, you can view more options by going down to One-Click Search Engines and then click Find more search engines to see the other alternatives.

Startpage seems to be a pretty good option that gives you good results and still respects your privacy (additional setup instructions here).

Firefox also has a guide on modifying your search engine settings.

Enable tracking protection

With the newer versions of Firefox, you can now enable tracking protection to always be active, rather than only in private browsing mode. To do this, go to Menu > Options > Privacy and Security > Tracking Protection and then click Always.

firefox tracking protection

You can also enable tracking protection in Firefox for Android by going to Menu > Settings > Privacy > Tracking Protection and then click the box to enable.

This may also improve browser performance.

Do Not Track (request)

Firefox also has an option to request that websites “do not track” you online. This is simply an HTTP header field that you can easily enable. However, the key word here is request, because this is not actually blocking anything. We have also learned that many websites simply ignore these requests.

On a positive note, there are some websites respecting do not track requests (including Restore Privacy, which uses Matomo instead of Google Analytics). To enable Do Not Track simply go to Menu > Options > Privacy & Security > Tracking Protection and then under ‘Send websites a “Do Not Track” signal…’ select Always.

firefox do not track

You can enable this in Firefox Android by going to Menu > Settings > Privacy > Do not track.

Now we will move onto the about:config settings.

Firefox About:Config settings

Aside from the general Menu settings we used above, you can also make a number of different modifications using about:config.

Note: If you made all of the changes above, you may noticed that some of these settings are already updated in about:config. We will cover the different about:config since some people prefer to modify settings in this area, rather than through the general Menu.

To access these configuration settings, simply enter about:config into the URL bar and hit enter. You will then be prompted with a warning screen stating “This might void your warranty”. Just click “I accept the risk” to continue.

about config firefox privacy

After proceeding, you will see a large list of preferences, which each include a status, type, and value.

These preferences will be listed in alphabetical order and easily searchable from the search bar near the top.

firefox about config changes

Modifying preferences – You can modify any of these Firefox preferences by simply double clicking the preference name. If the preference is a “boolean” type, then double clicking will change the value to true or false. If the preference is an “integer” or “string” type, double clicking will open a box to change the value.

media.peerconnection.enabled (WebRTC)

WebRTC stands for “Web Real-Time Communication” and it allows for voice, video chat, and P2P sharing through your browser. Unfortunately, this capability can also expose your real IP address through browser STUN requests, even if you are using a VPN service.

To disable WebRTC in Firefox simply enter media.peerconnection.enabled into the search bar and then double click the value to change it to false.

firefox webrtc

Note – Aside from Firefox, the WebRTC vulnerability also affects Chrome and Opera browser. Check out the WebRTC leaks guide for steps to block or disable WebRTC in all browsers.


Changing this preference to true will help to make Firefox more resistant to browser fingerprinting.

Note: There are many factors that go into browser fingerprinting and the ability of an adversary to identify you. Another option is to use the Tor browser.


Changing this to true will isolate cookies to the first party domain, which prevents tracking across multiple domains. First party isolation also does much more than isolating cookies, it affects: cookies, cache, HTTP Authentication, DOM Storage, Flash cookies, SSL and TLS session resumption, Shared Workers, blob URIs, SPDY and HTTP/2, automated cross-origin redirects,, auto-form fill, HSTS and HPKP supercookies, broadcast channels, OCSP, favicons, mediasource URIs and Mediastream, speculative and prefetched connections.

This preference was added in late 2017 as part of the Tor Uplift Project.


Setting this to false will disable geolocation tracking, which may be requested by a site you are visiting. As explained by Mozilla, this preference is enabled by default and utilizes Google Location Services to pinpoint your location. In order to do that, Firefox sends Google:

  1. your computer’s IP address
  2. information about “nearby wireless access points”
  3. a random client identifier, which is assigned by Google

Before this data is sent to Google, you would first get a request by the site you are visiting. Therefore you do have control over this, even if geo remains enabled.


Setting this preference to false will block websites from being able to track the microphone and camera status of your device.


This is an integer type preference that you should set to a value of 1. This preference disables cookies and has the following values:

  • 0 = Accept all cookies by default
  • 1 = Only accept from the originating site (block third-party cookies)
  • 2 = Block all cookies by default

You can get more information on this preference from the Mozilla knowledge base.


This is another integer type preference that you should set to a value of 2. This preference determines when cookies are deleted. Here are the different options:

  • 0 = Accept cookies normally
  • 1 = Prompt for each cookie
  • 2 = Accept for current session only
  • 3 = Accept for N days

With a value of 2, websites you visit should work without any problems, and all cookies will be automatically deleted at the end of the session. You can get more information on this preference from the Mozilla knowledge base.


Setting this preference to true will disable Firefox from “prefetching” DNS requests. While advanced domain name resolution may slightly improve page load speeds, this also opens you up to privacy and security threats, as described in this paper.

You can get more information on this preference here.


Similar to prefetching DNS requests above, setting this preference to false will prevent pages from being prefetched by Firefox. Mozilla has deployed this feature to speed up web pages that you might visit. However, it will use up resources and poses a risk to privacy. This is another example of performance at the price of privacy.

You can get more information on network.prefetch here.


WebGL is a potential security risk, which is why it is best disabled by setting webgl.disabled to true. Another issue with WebGL is that it can be used to fingerprint your device.

You can get more information on the WebGL issue here and here.

A note on “safe browsing” preferences

There are many recommendations to disable the Safe Browsing feature in Firefox due to privacy concerns and potential Google tracking. However, these concerns are based on an older version of the Safe Browsing feature, which would utilize “real-time lookup” of website URLs. This method has not been in use since 2011 – explained further here.

If a URL is needed, Firefox takes the following precautions to protect user privacy, as explained by François Marier, a security engineer for Mozilla:

  • Query string parameters are stripped from URLs we check as part of the download protection feature.
  • Cookies set by the Safe Browsing servers to protect the service from abuse are stored in a separate cookie jar so that they are not mixed with regular browsing/session cookies.
  • When requesting complete hashes for a 32-bit prefix, Firefox throws in a number of extra “noise” entries to obfuscate the original URL further.

Therefore I would conclude that disabling Safe Browsing would give you no tangible privacy benefits, while also being a security risk. That being said, if you still want to disable this feature, here’s how:

  • browser.safebrowsing.phishing.enabled = false
  • browser.safebrowsing.malware.enabled = false

Firefox privacy and security add-ons

There are some great Firefox browser add-ons that will give you more privacy and security.

Note: When looking for Firefox add-ons, be sure to consider what you need in relation to the preferences you modified above. Some add-ons will be redundant and not necessary depending on your Firefox preferences and the other add-ons you are using.

In combination with the preference changes above, my top three recommendations for privacy add-ons would be:

  • uBlock Origin
  • HTTPS Everywhere
  • Decentraleyes

All three of these add-ons compliment the preferences listed above, are easy to use, and will probably not break websites you visit.

Another great add-on is Cookie AutoDelete. However, if you have already modified your cookie preferences in about:config as described above, then this add-on is not necessary.

uBlock Origin

ublock originuBlock Origin is an efficient, light-weight blocker that filters both ads and tracking. It has risen to popularity as a powerful alternative to Adblock Plus, which allows “acceptable ads” that many users disdain. One added benefit of uBlock Origin is that it can significantly improve performance and page load speed.

Another great feature with uBlock Origin is the ability to whitelist certain websites. Given that many sites will block access if they detect an ad-blocker, the ability to whitelist will come in handy. uBlock Origin is free and entirely open source.

HTTPS Everywhere

https everywhere firefoxHTTPS Everywhere is a good Firefox add-on that basically forces an HTTPS connection with the websites you visit – provided HTTPS is available for the site. This gives you more security and privacy, due to encryption.

Fortunately, more and more websites are implementing HTTPS, so this is becoming less of an issue. Nonetheless, HTTPS Everywhere is still a good add-on to use with Firefox.

You can get more information on HTTPS from Electronic Frontier Foundation, which is behind the creation of this add-on.


decentraleyes firefoxDecentraleyes is an interesting Firefox add-on that protects you against tracking via content delivery networks that are operated by third parties. While CDNs do help improve website load time and performance, they are usually offered for free by third-parties that will use the CDN to track your browsing. These third parties include Google, Microsoft, Facebook, Cloudflare, Yandex, Baidu, MaxCDN, and others.

Decentraleyes solves this problem by hosting CDN resources locally. As described on their self-hosted GitLab repository, Decentraleyes “intercepts traffic, finds supported resources locally, and injects them into the environment” thereby preventing CDNs from tracking users.

Cookie AutoDelete

This browser add-on may not be necessary with Firefox if you have made the changes above to preferences, which will automatically erase cookies that are no longer needed for the website you are viewing.

However, if you’d rather use an add-on instead of making these about:config changes, then Cookie AutoDelete is the way to go. It erases cookies that are no longer needed, thereby protecting you from tracking.

Privacy Badger

Privacy Badger is another add-on from Electronic Frontier Foundation that blocks spying ads and trackers. One drawback with Privacy Badger is that it only blocks third-party sites. Because it considers Google Analytics first-party site, it will not be blocked. Another drawback is that it does not actually use a filter list. Instead, it basically learns as you use it.

On a positive note, Privacy badger is very easy to use and will go a long way to giving you more privacy with general browsing. It can be used in combination with uBlock Origin, although there will be some overlap in terms of functionality.


uMatrix is an advanced add-on that gives you control over requests that may be tracking you on the websites you visit. It is made by the same people behind uBlock Origin. One advantage with uMatrix is that it is very customizable.

One drawback with uMatrix is that it can be difficult and time-consuming to get it configured for regular, day-to-day browsing. However, if you want a very powerful blocker, and you don’t mind having to tinker with this plugin, then give uMatrix a shot.


NoScript is a script-blocker that allows you to determine exactly which scripts run on specific websites. While it does give you control, NoScript can be a real pain to get configured properly. It breaks many websites, which requires you to tweak and configure the options. If you are already using uBlock Origin, or uMatrix, then you probably don’t need to be using NoScript.

This is definitely not an add-on for the casual user or those who don’t have the patience to devote some time into configuration.

Additional resources

Below are some additional resources for configuring Firefox to give you more privacy and security:

  • user.js Firefox hardening – As explained on their GitHub page, this is a “configuration file that can control hundreds of Firefox settings. For a more technical breakdown and explanation, you can read more on the overview wiki page.” Their Wiki page is also full of great information.
  • Privacy Settings – This is a Firefox add-on to give you easy access and control of the built-in privacy settings in your browser.
  • Firefox Profilemaker – FFprofile helps you to create your own Firefox profile with the default privacy and security settings to fit your needs.

Firefox privacy conclusion

Firefox remains the best all-around, mainstream browser on the market for privacy.

While many of the configurations and add-ons we discussed in this article will go a long way to giving you more privacy, there is one issue that remains: concealing your IP address and location. To do this a good VPN is necessary. The Tor network also achieves this end, but it comes with the drawbacks of slow speeds and other risks

Also keep in mind that a secure, privacy-focused browser is just one of many tools to keep you safe online. Check out the privacy tools page for additional tips and recommendations to restore your privacy.

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