Firefox | A guide to configure Mozilla Firefox web browser and make it more privacy-focused and more.

Introduction

Your browser knows more about you than almost any other software on your computer. By default, Firefox balances convenience and privacy but leans toward functionality—leaving features enabled that quietly collect data or expose your identity to trackers.

This guide transforms Firefox into a significantly more privacy-focused browser by configuring: Enhanced Tracking Protection (Strict mode), automatic data cleanup on browser close, telemetry disabled, HTTPS-Only Mode, locked-down permissions, and hardened connection security. Settings mirror Librewolf's defaults applied manually for full control.

Prioritized approach: This guide favors privacy over convenience and security over usability. For the most part, it aligns with LibreWolf's default hardened configuration on Linux systems, with selective adjustments to improve site compatibility and daily usability.

＋ What you'll gain:

Stronger tracking protection via ETP Strict mode—blocks cross-site cookies, social media trackers, cryptominers, and fingerprinting scripts
Automatic data cleanup on browser close—cookies, cache, and form data are wiped every session
Telemetry disabled across the board—stops Firefox from sending usage data to Mozilla
Hardened connection security with HTTPS-Only Mode enabled
Locked-down permissions preventing websites from accessing location, camera, microphone, notifications, and more

－ Expect These Trade-offs:

Sites may break due to Enhanced Tracking Protection blocking certain elements
You must log in to accounts every session (cookies cleared on close)
Some websites won't function perfectly under Strict mode

Recommendations Before You Begin:

Password manager essential: Bitwarden, Proton Pass, or for a local solution, KeePassXC.
Backup your profile and create a new one (see Backup your profile section)
Prefer out-of-the-box? For similar privacy without manual setup, consider Librewolf, Mullvad Browser, or if you need even more anonymity, Tor Browser.

Legend

This is a comment or note from the author.
This is what you need to edit or focus on.
disabled option / feature turned off.
enabled option / feature turned on.

Access Firefox Settings

Open the menu by clicking the ☰ burger icon at the top right, then click on Settings.
Or you can type about:preferences in the address bar (CTRL + L).

Home and startup

Startup

Open previous windows and tabs
Always check if Firefox is your default browser

Homepage

Prefer a clean Blank Page on New windows and New tabs. Or use custom URLs. Or even better, if you know HTML, make your own home page! This is a personal choice.

New windows

← Blank page or your own custom homepage.

New tabs

← Blank page and use your bookmarks instead.

Firefox Home

Search

Default search engine

Prefer to switch to a more privacy-friendly search engine like DuckDuckGo, Startpage or Brave Search ~~rather than Google~~ as the default search engine. You can use Bangs shortcuts if needed.

Show search terms in the address bar on results pages ← Disable

🛈 TIP & PRIVACY-PRESERVING SEARCH ENGINES

It is possible to add a search engine from a website by right-clicking the address bar and selecting 'Add "[Website Name]"'. It will then appear in your Default Search Engine selection menu within Settings, allowing you to choose it as your default.

Give it a try with Brave Search! Is the best if you want balance of privacy, independence, and result quality. It is the most future-proof option as it builds its own map of the web rather than renting one from Google or Microsoft.

Brave Search A privacy-preserving search engine based in the US. Search results are based on its own index. DuckDuckGo A privacy-preserving search engine based in the US. Search results are mainly based on Bing. Startpage A privacy-preserving search engine based in the Netherlands. Search results are mainly based on Google.

Search engine suggestions

Show search suggestions ← Disable
- Show search suggestions before browsing history in address bar results ← Disable
- Search suggestions in private windows ← Disable
- Trending search suggestions ← Disable

Address bar

Choose which suggestions display in your address bar

Browsing history ← Disable
Bookmarks ← Optional
Open tabs ← Disable
Shortcuts ← Disable
Recent searches ← Disable
Suggest search engines to use ← Disable
Quick actions ← Optional

Privacy and security

Enhanced Tracking Protection

Firefox ETP Strict mode offers stronger privacy than Standard mode by blocking a wider range of tracking mechanisms across all browsing sessions. It blocks all cross-site cookies, tracking content in all windows (not just private ones), social media trackers, cryptominers, and fingerprinting scripts, significantly reducing the ability of third parties to monitor your activity. It also includes Bounce Tracking Protection and query parameter tracking mitigation, which stop stealthy redirect-based tracking. While this may occasionally affect site functionality, Firefox uses WebCompat shims to maintain usability without compromising privacy. For users prioritizing maximum protection, Strict mode provides a robust, multi-layered defense against pervasive online tracking.

We recommend that you set the Enhanced Tracking Protection on Strict.

Click Advanced settings
Select Strict

Strict
Stronger protections that block more trackers, but may cause some sites to break.
- Fix major site issues (recommended) ← Disable
  Helps load sites and features by unblocking only essential elements that may contain trackers. Covers most common problems.
  - Fix minor site issues ← Disable
    Restores things like videos in an article or comment sections by unblocking elements that may contain trackers. This can reduce site issues but offers less protection. Must be used with fixes for major issues.

Browsing data

Manage your cookies, history, cache, website data, and more.

Click to open Clear browsing data and cookies window
Set When on Everything
Check the options below

Clear browsing data ❱

Clear browsing data and cookies

When:

Browsing & download history ← Optional

Clears site and download history

Cookies and site data ← Enable

May sign you out of sites or empty shopping carts

Temporary cached files and pages ← Enable

Clears items that help sites load faster

Saved form info ← Enable

Clears things like names, emails, and other items you enter in forms

Site settings ← Optional

Resets your permissions and site preferences to original settings

Clear data for specific sites ❱

Manage exceptions ❱

Choose how specific sites handle cookies and sites data

Clear cookies and site data every time you close Firefox ← Enable

History

Choose what you want Firefox to remember when you close the browser.

Remember history

Customize history

Choose what you want Firefox to remember ❱

Advanced settings (History)

Customize what you want Firefox to remember when you close the browser.

Always use private browsing mode ← Disable
Remember browsing and download history ← Optional
Remember search and form history ← Disable
Clear history when Firefox closes ← Enable

Settings... ❱

Clear browsing data and cookies (History)

Automatically clear all checked items when Firefox closes.

Browsing & download history ← Optional

Clears site and download history
Cookies and site data ← Enable

May sign you out of sites or empty shopping carts
Temporary cached files and pages ← Enable

Clears items that help sites load faster
Saved form info ← Enable

Clears things like names, emails, and other items you enter in forms
Site settings ← Optional

Resets your permissions and site preferences to original settings

Never remember history

Every window acts like a private window. When on, extensions need to be allowed.

Additional protections

We are not sure about these options, so we will go with the default to avoid standing out.

Tell websites not to sell or share my data ← Default

Suggest Firefox Relay email masks ← Default

Hides your real email address to protect your inbox from spam.

DNS over HTTPS

Domain Name System over HTTPS (DoH) encrypts site lookups so it’s harder for your internet provider or others to see what websites you’re about to visit.

We recommend that you set the Domain Name System (DNS) over HTTPS to Off, and use the one you set on your system or router level. DoH should be at operating system level or router level, not browser based! Or you can use a Custom provider like the example below, if you dont know what to do, both options are valid.

Custom

Always use secure DNS with control over your provider and fallback behavior.

Advanced settings ❱

Advanced settings (DNS over HTTPS)

Domain Name System over HTTPS (DoH) encrypts site lookups so it’s harder for your internet provider or others to see what websites you’re about to visit.

Default

Use secure DNS in regions where it’s available

Custom

Always use secure DNS with control over your provider and fallback behavior

Always warn me if secure DNS isn’t available

Choose provider:

Off

Use your default DNS resolver

🛈 RELIABLE DNS PROVIDERS

You can enter the url of one of these reliable DNS Providers in the Custom field.

PROVIDER

URL

FEATURES

AdGuard https://dns.adguard.com/dns-query ad blocking, tracking protection. LibreDNS https://doh.libredns.gr/noads no logging, ad blocking, tracking protection. Mullvad https://all.dns.mullvad.net/dns-query no logging, block ads, trackers, malwares, adult, gambling, social media. Quad9 https://dns.quad9.net/dns-query no logging, malware, phishing, spyware, and botnets protection.

Connection and software security

See how connections stay secure, harmful software is blocked, and websites are verified.

Advanced settings ❱

HTTPS-Only Mode

Only allows secure connections to websites. Firefox will ask before connecting insecurely.

Enable HTTPS-Only Mode in all windows

Enable HTTPS-Only Mode in private windows only

Don’t enable HTTPS-Only Mode

Firefox may still upgrade some connections

Privacy panel settings

Get help protecting your info online in Firefox.

We are not sure about these options, so we will go with the default to avoid standing out.

Show breach messages ← Default

Deceptive content and dangerous software protection (Safe Browsing)

Dangerous sites and downloads can put your data and device at risk. Firefox automatically blocks them, and warns you about risky or unwanted software.

We disable Deceptive Content and Dangerous Software Protection, also known as Safe Browsing, by default to avoid sending data to Google, as it conflicts with our privacy-first approach. Instead of relying on third-party services, we prioritize user privacy and recommend using privacy-respecting tools like uBlock Origin for protection. For users who want stronger malware and phishing defenses, options like the free Quad9 DNS Service are available.

Block dangerous and deceptive content ← Disable
- Block dangerous downloads ← Disable
- Warn you about unwanted and uncommon software ← Disable

Passwords and autofill

Passwords

We recommend to disable the Firefox password manager and use a better and more secure solution like Bitwarden, or Proton Pass which are primarily cloud-based password managers that sync encrypted data across devices. For a local-only password manager, KeePassXC is the best option.

Ask to save passwords ← Disable

Save and autofill usernames and passwords ← Disable

Suggest strong passwords ← Disable

Payment methods

It is not a good idea to have information like credit or debit cards stored in a browser, so let's disable it.

Save and autofill payment info ← Disable

Addresses and more

It is not a good idea to have such information stored in a browser, so let's disable it.

Save and autofill addresses ← Disable

Tabs and browsing

Tabs

Containers

Containers is a good feature, see Firefox Containers section.

Use Container Tabs ← Default in Firefox 153

Recommendations

Recommend extensions as you browse ← Disable

Recommend features as you browse ← Disable

AI Controls

AI features are optional; it depends if you use them or not. For the purpose of this guide, we prefer disable and block Firefox AI enhancements (Set the switch to the right to block).

Block AI enhancements

Blocking means you won’t see new or current AI enhancements in Firefox, or pop-ups about them. Get more details about what’s included and how to control traditional machine learning features, like search suggestions and recommendations.

Permissions and data

We suggest to block ALL permissions access and new requests to get access to our device.
(Location, Camera, Microphone, Notifications, Autoplay Audio & Video, Virtual Reality).
Check "Block pop-up windows" and "Warn you when website try to install add-ons".
Click on every permission and Block them in their own panel.

"Firefox data collection and use" options control Firefox telemetry, disable all of them will turn off telemetry.

Permissions

Manage what websites can access, control, or trigger.

Location ❱

Settings - Location Permissions

Block new requests asking to access your location ← Enable

This will prevent any websites not listed above from requesting permission to access your location. Blocking access to your location may break some website features.

Camera ❱

Settings - Camera Permissions

Block new requests asking to access your camera ← Enable

This will prevent any websites not listed above from requesting permission to access your camera. Blocking access to your camera may break some website features.

Microphone ❱

Settings - Microphone Permissions

Block new requests asking to access your microphone ← Enable

This will prevent any websites not listed above from requesting permission to access your microphone. Blocking access to your microphone may break some website features.

Notifications ❱

Settings - Notifications Permissions

Block new requests asking to allow notifications ← Enable

This will prevent any websites not listed above from requesting permission to send notifications. Blocking access to your notifications may break some website features.

Autoplay ❱

Settings - Autoplay Permissions

Default for all websites:

Virtual Reality ❱

Settings - Virtual Reality Permissions

Block new requests asking to access your virtual reality devices

This will prevent any websites not listed above from requesting permission to access your virtual reality devices. Blocking access to your virtual reality devices may break some website features.

Block pop-ups and third-party redirects ← Default

Show warning when websites try to install extensions ← Default

Firefox data collection and use

Uncheck all "Firefox Data Collection and Use" options below to disable Firefox telemetry.

Send technical and interaction data to Mozilla ← Disable

Data reporting is disabled for this build configuration
- Allow personalized extension recommendations ← Disable
  
  Get extension recommendations to improve your browsing experience.
  
  Allow Firefox to run feature studies ← Disable
  
  Firefox randomly selects users to test features, which helps improve quality for everyone.
Allow Firefox to improve features, performance, and stability between updates ← Disable

Changes will be rolled out remotely.
Send daily usage ping to Mozilla ← Disable

This helps Mozilla to estimate active users.
Automatically send crash reports ← Disable

This helps Mozilla diagnose and fix issues with the browser. Reports may include personal or sensitive data.

Conclusion

Congratulations on taking proactive steps toward reclaiming your digital privacy. By applying these configurations, you've transformed Firefox from a convenient browser into one of the most privacy-respecting options available, without needing to switch to an entirely different fork or lose compatibility with modern websites.

Remember: Privacy is not a destination, it's a practice. Websites evolve new tracking methods constantly, and keeping your configuration effective means staying informed and adjusting as needed.

Keep extensions minimal: Each extension adds attack surface and can leak data.
Update Firefox regularly: Security patches fix newly discovered vulnerabilities.
Use a password manager: Essential when sessions expire frequently. Bitwarden, Proton Pass and KeePassXC are good solutions.

Final thoughts:

This guide prioritizes privacy over convenience and favors security at the expense of usability. If you find some features too disruptive, revisit individual settings and adjust them to your comfort level, partial hardening is still better than default exposure. The ultimate goal isn't perfection; it's awareness and intentional control over what data you share online.

For continued learning, explore the linked resources below or check out arkenfox user.js for deeper about:config customizations if you know what you're doing.

Your data belongs to you. Guard it accordingly.

Additional Resources:

Advanced Settings (about:config)

⚠ Use advanced settings to customize Firefox deeper or enable/disable hidden features.
For those who know what they are doing!

To access Firefox advanced settings, type about:config in the address bar (CTRL + L).

Examples:

Action

Preference

Recommended Value

Disable WebRTC media.peerconnection.enabled false Disable WebGL webgl.disabled true Disable from “prefetching” DNS requests network.dns.disablePrefetch true Prevent pages from being prefetched network.prefetch-next false Prevents websites from getting notifications if you copy, paste, or cut something from the page. dom.event.clipboardevents.enabled false

Explore the information from the arkenfox user.js at arkenfox gui.

Firefox user.js

A user.js is a configuration file that controls Firefox preferences, allowing users to harden privacy, security, and performance settings by overriding default behaviors at startup. It is read by Firefox upon launch, ensuring that specific about:config changes persist across sessions and are not overwritten by browser updates or Mozilla telemetry.

To install a user.js file, locate your Firefox Profile Directory (accessible via about:support → " Profile Directory "), and place the user.js file directly in that folder. Restart Firefox for the changes to take effect. Note that installing a user.js may clear browsing history, caches, and saved passwords if the template enforces strict privacy defaults.

Our user.js
[!] Review and adapt it to your needs before using it!

Add-ons / Extensions

⚠ The less extensions you have, the better!

Extensions are like apps for Firefox. They add features to Firefox to make browsing faster, safer, or just plain fun.

Below is a selection of what we think that are the best privacy-related extensions of their category.
We pick uBlock Origin as the best internet content and ad blocker, a must-have!

AdGuard AdBlocker | AMO | Unmatched adblock extension against advertising and pop-ups. Blocks ads on Facebook, Youtube and all other websites.
AdGuard VPN | AMO | Makes the Internet open and your data safe. Topnotch VPN from the creators of famous ad blocker.
Bitwarden | AMO | Bitwarden is a free and open-source password management service that stores sensitive information such as website credentials in an encrypted vault.
KeePassXC | AMO | Official browser plugin for the KeePassXC password manager (https://keepassxc.org).
LibRedirect | AMO | Redirects YouTube, Twitter, Instagram... requests to alternative privacy friendly frontends and backends.
Proton Pass | AMO | Free and unlimited password manager to keep your login credentials safe and manage them directly in your browser.
Proton VPN | AMO | Secure your internet and protect your online privacy in one click.
uBlock Origin | AMO | uBlock Origin is a free and open-source, cross-platform browser extension for content-filtering, including ad-blocking.

Backup your profile

Before changing your settings, it is strongly recommended that you backup your profile and start a new profile.

To backup your profile you need to access the profiles manager page by typing: about:profiles into the address bar.

Click on Open Folder on the Root Directory. There are some important files you want to keep.

FILE

DESCRIPTION

cookies.sqlite Store cookies between sessions. key4.db Contains a key used to encrypt and decrypt saved passwords. logins.json Stores the encrypted names and passwords. places.sqlite Stores the annotations, bookmarks, favorite icons, input history, keywords, and browsing history.

Firefox Containers

Firefox Containers ( about:preferences#containers ) are a privacy and security feature that allows users to isolate browsing data, such as cookies, login sessions, and local storage, into separate, color-coded tabs within a single browser window. Each container acts as an independent environment, preventing websites from tracking your activity across different contexts or mixing your online identities.

Key Benefits

Multi-Account Management: Users can stay logged into multiple accounts on the same website simultaneously (e.g., a personal Gmail and a work Gmail) without needing to log out or use separate browser profiles.
Enhanced Privacy: By isolating cookies and site data, Containers prevent advertisers and social networks from correlating your browsing habits across different sites, effectively limiting cross-site tracking.
Organized Workflow: Activities can be categorized into distinct spaces like Personal, Work, Banking, and Shopping, each marked with a unique color. This visual separation helps reduce distractions and prevents accidental data leaks between professional and personal tasks.

As of Firefox version 153 (released July 2026), this feature is enabled by default, offering four pre-configured containers out of the box and eliminating the need to manually install the former Multi-Account Containers extension.

🛈 To access Firefox Containers settings

☰ Settings → Tabs and browsing → Tabs → Contaimers → Manage settings
Or type about:preferences#containers in the address bar (CTRL + L)

Links

Some useful links.