ff-diff

ff-diff is a simple node script to compare changes in user.js preference files between two versions of Firefox. You don't need to mess with your firefox instance.

Features:

• Compares user.js files from two specified Firefox versions
• Automatically downloads official Firefox binaries
• Highlights differences without requiring a local Firefox installation

Requirements:

• Internet connection (for downloading Firefox binaries)
• node >= 22 and npm
• tar

Installation (NPM)

npm i -g ff-diff

Usage

$ ff-diff
Usage:
  ff-diff clean [--keep <version1>,<version2>] [--keep-archives] [--keep-sources]
  ff-diff <version1> <version2> [--clean-archives] [--clean-sources] [--do-not-print-diffs-in-console] [--save-diffs-in-file] [--compare-userjs <path>]

Example:

ff-diff 137.0 138.0

Develop

Clone this repository:

git clone https://github.com/martabal/ff-diff.git
cd ff-diff
npm ci

Run the comparison script:

npm run ff-diff <version1> <version2>

for example:

npm run ff-diff 137.0 138.0

If you use a custom user.js. You can check if some of the keys are removed/changed with the argument --compare-userjs <path_to_your_userjs>.

Clean

The Firefox sources will be downloaded into the dist/ directory. By default, the script keeps the archives and the sources extracted from the archives. If you want to remove them, you can execute the script with the --remove-archives --remove-sources arguments. But you can also use the script npm run clean to delete all archives and sources in dist/. If you want to use specific version you can use:

npm run ff-diff clean -- --keep <version1>,<version2>

If you want to only keep archives you can use npm run clean -- --keep <version1>,<version2> --keep-archives or npm run clean -- --keep <version1>,<version2> --keep-sources if you want to keep the sources

Note

The script may take some time to run depending on your connection speed.

Example of a generated diffs: