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Willie Shen edited this page Sep 15, 2026 · 3 revisions

Combinedfox User.js

User.js

A user.js file is a Javascript file in your profile folder used to set preferences for that profile when Firefox starts. You can update the user.js while Firefox is open, it is only read when Firefox starts. If a preference set in user.js is changed in about:config, it will be overridden back to the value set in user.js when Firefox starts next time. Each preference must follow Mozilla's syntax, which is user_pref("prefname", value); (note that the semicolon is required), where prefname is a string, and there are three main types of values:

  • Boolean: true or false without quotes.
  • Integer: a number without quotes, e.g., 6.
  • String: a string quoted with "", e.g., "https://www.duckduckgo.com".

A line starting with // is a single-line comment. Lines quoted with /* and */ are a multi-line comment. Comments are skipped when loading.

A user.js applies prefs in the order they are written. If a preference is listed multiple times, then the last value would override the others.

Refer to arkenfox wiki 2.1 User.js for more information.

Contents

combinedfox user.js contains the following contents applied in the following order (the later overrides the former):

First Run

It is highly recommended to read combinedfox wiki and arkenfox wiki and recommended to read all files listed in Contents before using combinedfox user.js.

To go to the profile folder, go to about:support in Firefox, find the Profile Directory or Profile Folder item in the Application Basics, which is typically about 9th to 11th, and click Open Directory or Open Folder button.

  1. To apply combinedfox user.js, you can either use a new profile, which can be created in the Profiles entry or the entry whose name is current profile name of Firefox application menu at the top right, or an existing profile. If you are using an existing profile, Backup first.
  2. Prepare Scripts
  3. Overrides
  4. Run the Updater

Update

  1. Check for the changelogs and diffs of arkenfox, release notes of Betterfox, and combinefox wiki changes.
  2. Run the Updater.
  3. Run the prefsCleaner.

Run the following one-liner in the profile folder to run the updater and prefsCleaner for macOS and Linux. Execute it only if you know what you're doing.

./updater.sh -su && ./prefsCleaner.sh -s

Backup

The easiest and complete way to backup is to copy and paste your entire profile folder when Firefox is closed. Just backing up prefs.js file is not enough and not recommended.

It is recommended to rename your copied folder to something meaningful and keep the original name (for an easy rollback). For example, if the profile folder is called jiu9k8gm.default, a backup copy might be called jiu9k8gm.default-backup, jiu9k8gm.default-pre-combinedfox, or jiu9k8gm.default-$(date +"%Y-%m-%d_%H%M").

It is recommended to backup before any big change to a profile, such as applying a user.js.

Be aware that this is your entire profile, so keep it secret. Rolling back will also rollback cookies, saved passwords, bookmarks, extensions, etc.

Prepare Scripts

This is only needed for the first run. When updating, the existing scripts will update themselves. Thus there is no need to re-download them during updates unless they are missing.

MacOS and Linux

Download the following files to the profile folder

wget https://github.com/Willie169/combinedfox/raw/refs/heads/main/prefsCleaner.sh
wget https://github.com/Willie169/combinedfox/raw/refs/heads/main/updater.sh

and make them executable:

chmod +x prefsCleaner.sh
chmod +x updater.sh

Windows

Download the following files to the profile folder:

Overrides

combinedfox includes hundreds of preference changes from various sources. Since everybody has their own mileage, threat model, and habits, almost everyone will need some overrides.

How to Override

Remember that if a preference is listed multiple times, then the last value would override the others. Your overrides are applied the last, which means that they will override values in combinedfox and be the final values.

Create your overrides file in the profile folder. The default custom overrides file name is user-overrides.js, you can also use other file names, use multiple files, or use all files with extension .js in a folder by specifying them later when running the updater during Update.

What to Override

It is recommended to read the files listed in Contents and reverse changes you don't want in your overrides file and read

arkenfox and combinedfox both set Enhanced Tracking Protection (ETP) Strict mode with user_pref("browser.contentblocking.category", "strict"); and overriding it is not supported.

Updater

Execute updater.sh for macOS and Linux and updater.bat for Windows. The scripts is modified from that of arkenfox with user.js download links changed to those of combinedfox. Thus, refer to arkenfox wiki 5.1 Updater [Options] for the instructions.

prefsCleaner

Execute prefsCleaner.sh for macOS and Linux and prefsCleaner.bat for Windows. Do not delete user.js before execution since the scripts depend on it. The scripts are copied from the branch of arkenfox that combinedfox is currently using. Thus, refer to arkenfox wiki 3.5 prefsCleaner for the instructions.

Next: 3. Extensions

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