Guide · Open source
How to use user.js: set up arkenfox Firefox privacy hardening
Updated · written with AI from the project's own documentation and checked against our catalogue data
A user.js is a configuration file that Firefox reads at startup to change its settings. The arkenfox user.js is a large template of such settings aimed at reducing tracking and fingerprinting while improving security. This guide explains what it is, how to get the template, and how to handle the breakage it admits will happen, so you can use it on desktop Firefox with fewer surprises.
arkenfox user.jsarkenfox/user.js · ★ 13k · MIT Install options & downloads Quick start
- 1Confirm you use desktop Firefox. The template is made specifically for desktop Firefox. Check that this is the browser you plan to configure.
- 2Clone the repository. Run the git clone command from the README to download the arkenfox/user.js project from its official GitHub repository.
- 3Read the wiki. Read the project wiki, which the README says everyone should at least read, especially the pages on important settings.
- 4Review the settings. Open the template and check the settings you intend to apply, so you understand what each one changes.
- 5Apply and test. Apply the settings to Firefox, then test the sites and extensions you use to find any breakage.
- 6Revert what breaks. Undo the individual settings that cause problems, keeping the rest of the hardening in place where it works.
What a user.js file does in Firefox
A user.js is a configuration file that can control Firefox settings. Firefox reads it at startup and applies the settings it contains.
The arkenfox project describes its file as a template. It aims to provide as much privacy and enhanced security as possible and to reduce tracking and fingerprinting, while minimizing loss of functionality. The project states that breakage will still happen.
Get the arkenfox user.js template
The project's README gives a clone command to download the repository. Use only the official sources: the README warns not to trust other sites claiming to be arkenfox.
- Clone the repository with the command shown below.
- Use the repository or the interactive webpage linked in the README as your sources.
- Check the project's releases page for the current release files.
git clone https://github.com/arkenfox/user.jsRead the wiki before you apply anything
The README says everyone, experts included, should at least read the wiki, because it contains important information about a few user.js settings. The wiki also gives a more technical breakdown of how a user.js works.
Read the relevant wiki pages before you change settings you do not understand. Some settings have trade-offs that the template does not explain on its own.
Plan for breakage and know how to revert
The README says the template tries to minimize breakage but notes that it will happen. Sites may fail to load, and extensions may stop working. Expect to test sites after you apply the file.
When something breaks, adjust or revert the specific setting that caused it rather than abandoning the whole template. Keep track of what you changed so you can undo it.
- Test the sites and extensions you rely on after each change.
- Revert individual settings when a site breaks.
- Use the project's common questions and answers and stickies for known issues.
When not to use it, including Tor
The README says not to connect over Tor on Firefox. For Tor-level anonymity or accessing hidden services, it recommends the Tor Browser if your threat model calls for it.
The template is made specifically for desktop Firefox. The README says using it as-is in other Gecko-based browsers can be counterproductive, especially in the Tor Browser.
- Do not use it if you need sites and extensions to work without any breakage.
- Do not use it for Tor-level anonymity; use the Tor Browser instead.
- Do not apply it to other Gecko-based browsers.
What people use it for
- Reducing tracking and fingerprinting on a personal desktop Firefox profile
- Starting from a documented, widely referenced hardening template instead of writing settings from scratch
- Reviewing each setting in a large template to learn what Firefox options control privacy and security
- Testing which sites break under stronger privacy defaults and reverting only those settings
Frequently asked questions
What is a user.js file?
A user.js is a configuration file that Firefox reads at startup to change its settings. The arkenfox user.js is a template of such settings aimed at reducing tracking and fingerprinting while improving security.
How do I install arkenfox user.js?
The README gives a clone command: git clone https://github.com/arkenfox/user.js. After cloning, read the wiki and review the settings before applying them to desktop Firefox.
Is arkenfox user.js free?
The project is licensed under MIT, as shown in its README. The source does not mention pricing for any other part of the project.
Will arkenfox user.js break websites?
The README says the template minimizes loss of functionality and breakage, but notes that breakage will still happen. Test the sites you use and revert individual settings that cause problems.
Can I use arkenfox user.js with Tor Browser?
No. The README advises against connecting over Tor on Firefox, and says using the template as-is in the Tor Browser can be counterproductive. It recommends the Tor Browser itself if your threat model calls for Tor.
Does arkenfox user.js work on other browsers?
The README says the template is made specifically for desktop Firefox. It says using it as-is in other Gecko-based browsers can be counterproductive.
New agent skills, repos and AI tools — every week
The best new skills and open-source projects, the fastest-growing repos, and one free prompt. Five minutes to read. Unsubscribe anytime.
Our verdict
Use arkenfox user.js if you run desktop Firefox, want stronger privacy defaults, and are willing to read a settings file and test sites when something breaks. Pick something else if you need everything to work without breakage, or if you need Tor-level anonymity, where the project itself recommends the Tor Browser.
Install options & downloads