Firefox Privacy Hardening Guide 2026

Firefox offers exceptional privacy customization through its advanced settings, known as about:config. Unlike Chrome, which Google controls, Firefox is developed by Mozilla—a non-profit focused on privacy. This guide reveals specific configuration changes, essential extensions, and settings that transform Firefox into a privacy powerhouse in 2026.

Firefox Privacy Foundation

Firefox’s privacy advantage stems from:

• Open-source code auditable by security researchers
• No mandatory tracking (unlike Chromium browsers)
• Stronger cookie controls than competing browsers
• DNS over HTTPS (DoH) support for encrypted DNS
• Total Cookie Protection to prevent cross-site tracking
• Enhanced Tracking Protection enabled by default

Let’s unlock Firefox’s full potential.

Essential Privacy Settings

Start with Firefox’s built-in privacy settings:

Access Settings:

1. Click menu (hamburger icon) → Settings
2. Select Privacy & Security from left sidebar

Browsing Data:

• Set “History” to Use custom settings for history
• Check all boxes: Cookies, site data, cache, active logins
• Select Clear history when Firefox closes

Enhanced Tracking Protection:

• Change from “Standard” to Strict
• Strict blocks more trackers (some sites may break)
• Note broken sites and return to Standard if needed

Cookies and Site Data:

• Set to Reject all cookies (or All third-party cookies)
• Enable Clear cookies and site data when Firefox closes

HTTPS-Only Mode:

• Enable HTTPS-Only Mode in all windows
• Firefox forces HTTPS on all sites
• Enable exception handling for legacy sites

DNS Over HTTPS:

• Set to Max Protection if using Firefox’s DoH provider
• Or select custom provider (Cloudflare, Quad9, NextDNS)
• Encrypts DNS queries from ISP snooping

Permissions:

• Click Permissions section
• Location: Block (most sites don’t need location)
• Microphone: Block (enable per-site)
• Camera: Block (enable per-site)
• Notifications: Block (or remove all sites)

Advanced about:config Tweaks

about:config contains hundreds of settings. Open it by:

1. Type about:config in address bar
2. Click Accept the Risk and Continue
3. Use search box to find settings

Critical Privacy Settings:

Setting	Value	Purpose
privacy.trackingprotection.enabled	true	Block tracking
dom.disable_beforeunload	true	Prevent pop-ups on tab close
beacon.enabled	false	Block tracking beacons
browser.sessionstore.privacy_level	2	Don’t save session data
dom.event.clipboardevents.enabled	false	Block clipboard access
extensions.activeThemeID	firefox-compact-dark	Use compact UI
geo.enabled	false	Disable geolocation
browser.compactmode.show	true	Enable compact mode
network.http.referer.XOriginPolicy	2	Strict referrer policy

WebGL Fingerprinting Protection:

WebGL can reveal GPU information for device fingerprinting:

webgl.disabled = true

Or disable only WebGL renderer:

webgl.renderer.allow_reset = false

Canvas Fingerprinting:

canvas.poisondata = true

Geolocation:

geo.prompt.testing = false
geo.prompt.testing.allow_insecure = false

Device Motion Sensors:

device.sensors.enabled = false
device.sensors.motion.enabled = false
device.sensors.orientation.enabled = false

Telemetry Disable:

datareporting.policy.dataSubmissionPolicyAcceptedVersion = 0
datareporting.policy.dataSubmissionPolicyNotifiedTime = 0

DNS Prefetching:

network.dns.disablePrefetch = true

Prevents Firefox from resolving domains before you visit them.

Network Partitioning:

privacy.partition.network_state = true

Prevents cross-origin tracking through shared network state.

Essential Privacy Extensions

Firefox extensions enhance privacy beyond built-in features:

uBlock Origin (Adblocker)

Download from: addons.mozilla.org/firefox/addon/ublock-origin/

The best adblocker available. Configuration:

1. Click uBlock icon → Settings (gear icon)
2. Go to Filter lists tab
3. Enable all checked lists:
   • Malware domains
   • Peter Lowe’s ad/tracking server
   • EasyPrivacy
   • Fanboy’s Social Blocking
4. Go to Settings tab
5. Enable: Prevent WebRTC leak, Log network requests

Privacy Badger

Download from: addons.mozilla.org/firefox/addon/privacy-badger17/

Google-funded but independent tracker blocker:

• Shows detailed tracking information
• Blocks third-party cookies
• Complements uBlock Origin

HTTPS Everywhere

Download from: addons.mozilla.org/firefox/addon/https-everywhere/

Forces HTTPS on compatible sites:

• Enable Block all unencrypted requests
• Exceptions auto-added for sites that require HTTP

Container Tabs

Download from: addons.mozilla.org/firefox/addon/multi-account-containers/

Isolate cookies by website container:

1. Click icon → Create Container
2. Name it (Work, Personal, Banking)
3. Click website container button before visiting
4. Cookies isolated to that container only

Prevents Facebook from tracking you across the web.

ClearURLs

Download from: addons.mozilla.org/firefox/addon/clearurls/

Removes tracking parameters from URLs:

• Blocks Amazon affiliate links
• Removes utm_source parameters
• Cleans referral codes before navigation

Decentraleyes

Download from: addons.mozilla.org/firefox/addon/decentraleyes/

Blocks CDN tracking:

• Intercepts requests to content delivery networks
• Serves local alternatives
• Prevents CDN operator tracking

User-Agent Switcher

Download from: addons.mozilla.org/firefox/addon/user-agent-string-switcher/

Changes your user agent string:

1. Right-click page → Select User Agent
2. Choose Chrome, Safari, or random agents
3. Randomizes your browser fingerprint

Fingerprinting Protection

Modern sites fingerprint browsers through:

• Canvas fingerprinting
• WebGL queries
• Font enumeration
• Screen resolution
• Timezone information
• Language settings

Configure Firefox to mitigate:

privacy.trackingprotection.fingerprinting.enabled = true
privacy.trackingprotection.cryptomining.enabled = true
privacy.resistFingerprinting = true

Enable Resist Fingerprinting for maximum protection (may break some sites).

Search Engine Configuration

Change Firefox’s default search engine:

Built-in Options:

1. Go to Settings → Search
2. Scroll to Search Shortcuts
3. Change default to privacy-respecting engine:
   • DuckDuckGo: No tracking, quick answers
   • Ecosia: Eco-friendly, no tracking
   • Startpage: Privacy proxy for Google
   • Searx: Meta-search with optional anonymity

Add Custom Search Engines:

1. Right-click search box on any site
2. Select Add as Search Engine
3. Set shortcuts in Search settings

Blocking Malware and Phishing

Firefox includes integrated malware protection:

1. Go to Settings → Privacy & Security
2. Under Security, ensure all checked:
   • Deceptive Content and Dangerous Software Protection
   • Malware Protection
   • Extended Tracking Protection

This blocks known phishing and malware domains.

Sync Configuration

Firefox Sync encrypts synced data end-to-end:

1. Sign in to Firefox Account (or create one)
2. Click menu → Sync Settings
3. Uncheck items you don’t want synced:
   • History (often contains sensitive searches)
   • Bookmarks (unless you trust Mozilla)
   • Keep Passwords checked for security

End-to-end encryption means even Mozilla can’t read synced data.

Testing Your Configuration

Verify your privacy hardening:

1. Visit panopticlick.eff.org (from EFF)

   • Tests browser fingerprinting resistance
   • Shows how unique your browser is

2. Visit cover-your-tracks.eff.org (replacement for Panopticlick)

   • Tests tracking vulnerability
   • Checks WebGL, canvas, fonts

3. Visit browserleaks.com

   • Tests IP, DNS, WebGL, Canvas leaks
   • Shows what sites can detect

Performance Impact

Privacy hardening has minimal performance impact:

• Stricter tracking protection: 1-2% slower
• Extensions: 3-5% RAM overhead
• about:config tweaks: Negligible impact

Modern Firefox handles privacy features efficiently.

Regular Maintenance

Keep privacy intact with routine updates:

Weekly:

• Update Firefox (Settings → About Firefox)
• Update extensions (Add-ons menu)

Monthly:

• Review extension permissions
• Clear browsing data manually
• Check fingerprint at cover-your-tracks.eff.org

Quarterly:

• Audit about:config for setting resets
• Review DNS provider for issues
• Check for new recommended extensions

Conclusion

Firefox’s openness and privacy focus make it ideal for privacy-conscious users. By applying these settings, extensions, and about:config tweaks, you’ve configured one of the most private browsers available.

Remember: Privacy requires ongoing attention. Regularly update software, monitor settings for changes, and stay informed about new privacy features and threats.

Your privacy is worth the setup effort—maintain it diligently.