Firefox: Privacy Related "about:config" Tweaks

Preparation:

1. Enter "about:config" in the firefox address bar and press enter.
2. Press the button "I'll be careful, I promise!"
3. Follow the instructions below...

Getting started:

privacy.firstparty.isolate = true

A result of the Tor Uplift effort, this preference isolates all browser identifier sources (e.g. cookies) to the first party domain, with the goal of preventing tracking across different domains. (Don't do this if you are using the Firefox Addon "Cookie AutoDelete" with Firefox v58 or below.)

privacy.resistFingerprinting = true

A result of the Tor Uplift effort, this preference makes Firefox more resistant to browser fingerprinting.

privacy.trackingprotection.fingerprinting.enabled = true

[FF67+] Blocks Fingerprinting

privacy.trackingprotection.cryptomining.enabled = true

[FF67+] Blocks CryptoMining

privacy.trackingprotection.enabled = true

This is Mozilla's new built-in tracking protection. It uses Disconnect.me filter list, which is redundant if you are already using uBlock Origin 3rd party filters, therefore you should set it to false if you are using the add-on functionalities.

browser.cache.offline.enable = false

Disables offline cache.

browser.safebrowsing.malware.enabled = false

Disable Google Safe Browsing malware checks. Security risk, but privacy improvement.

browser.safebrowsing.phishing.enabled = false

Disable Google Safe Browsing and phishing protection. Security risk, but privacy improvement.

browser.send_pings = false

The attribute would be useful for letting websites track visitors' clicks.

browser.sessionstore.max_tabs_undo = 0

Even with Firefox set to not remember history, your closed tabs are stored temporarily at Menu -> History -> Recently Closed Tabs.

browser.urlbar.speculativeConnect.enabled = false

Disable preloading of autocomplete URLs. Firefox preloads URLs that autocomplete when a user types into the address bar, which is a concern if URLs are suggested that the user does not want to connect to. Source

dom.battery.enabled = false

The battery status of your device could be tracked.

dom.event.clipboardevents.enabled = false

Disable that websites can get notifications if you copy, paste, or cut something from a web page, and it lets them know which part of the page had been selected.

media.eme.enabled = false

Disables playback of DRM-controlled HTML5 content, which, if enabled, automatically downloads the Widevine Content Decryption Module provided by Google Inc. Details

DRM-controlled content that requires the Adobe Flash or Microsoft Silverlight NPAPI plugins will still play, if installed and enabled in Firefox.

media.gmp-widevinecdm.enabled = false

Disables the Widevine Content Decryption Module provided by Google Inc., used for the playback of DRM-controlled HTML5 content. Details

media.navigator.enabled = false

Websites can track the microphone and camera status of your device.

network.cookie.cookieBehavior = 1

Disable cookies

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

network.cookie.lifetimePolicy = 2

cookies are deleted at the end of the session

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

network.http.referer.trimmingPolicy = 2

Send only the scheme, host, and port in the Referer header

• 0 = Send the full URL in the Referer header
• 1 = Send the URL without its query string in the Referer header
• 2 = Send only the scheme, host, and port in the Referer header

network.http.referer.XOriginPolicy = 2

Only send Referer header when the full hostnames match. (Note: if you notice significant breakage, you might try 1 combined with an XOriginTrimmingPolicy tweak below.) Source

• 0 = Send Referer in all cases
• 1 = Send Referer to same eTLD sites
• 2 = Send Referer only when the full hostnames match

network.http.referer.XOriginTrimmingPolicy = 2

When sending Referer across origins, only send scheme, host, and port in the Referer header of cross-origin requests. Source

• 0 = Send full url in Referer
• 1 = Send url without query string in Referer
• 2 = Only send scheme, host, and port in Referer

network.trr.mode = 2

Use Trusted Recursive Resolver (DNS-over-HTTPS) first and if it fails, use the system resolver Source

• 0 = disabled by default, may change in the future
• 1 = use the faster resolver
• 2 = use DoH first, fallback to system resolver
• 3 = only use DoH. This may require network.trr.bootstrapAddress or using an IP address in network.trr.uri.
• 5 = explicitly disable DoH

network.trr.uri = CHANGEME

The address of your DNS-over-HTTPS provider, if you don't have one, check our encrypted DNS recommendations. It can also be changed in Settings, Network Settings, Enable DNS over HTTPS, Use Provider, Custom.

network.security.esni.enabled = true

Hide the address which you are requesting SSL certificate for if the server supports it. This requires DoH/TRR to be enabled even on Android 9+ when Private DNS is enabled.

webgl.disabled = true

WebGL is a potential security risk. Source

browser.sessionstore.privacy_level = 2

This preference controls when to store extra information about a session: contents of forms, scrollbar positions, cookies, and POST data. Details

• 0 = Store extra session data for any site. (Default starting with Firefox 4.)
• 1 = Store extra session data for unencrypted (non-HTTPS) sites only. (Default before Firefox 4.)
• 2 = Never store extra session data.

extensions.pocket.enabled = false

Disables Pocket completely.

network.IDN_show_punycode = true

Not rendering IDNs as their Punycode equivalent leaves you open to phishing attacks that can be very difficult to notice. Source

extensions.blocklist.url = https://blocklists.settings.services.mozilla.com/v1/blocklist/3/%20/%20/

Limit the amount of identifiable information sent when requesting the Mozilla harmful extension blocklist.

Optionally, the blocklist can be disabled entirely by setting extensions.blocklist.enabled to false for increased privacy, but decreased security. Source

Firefox user.js Templates

• ghacks-user.js - An ongoing comprehensive user.js template for configuring and hardening Firefox privacy, security and anti-fingerprinting.
• pyllyukko/user.js - This is a user.js configuration file to harden Firefox's settings and make it more secure.

Related Information

• ffprofile.com - Helps you to create a Firefox profile with the defaults you like.
• mozillazine.org - Security and privacy-related preferences.
• Privacy Settings - A Firefox add-on to alter built-in privacy settings easily with a toolbar panel.
• Firefox Privacy Guide For Dummies - Guide on ways (already discussed and others) to improve your privacy and safety on Firefox.