Create the files
Use the generator to choose pref, defaultPref or lockPref for each named preference. String values are quoted safely, booleans must be true or false, and integers must fit a signed 32-bit value. The generated firefox.cfg begins with a comment line because Firefox ignores its first line.
Install in Firefox
Place autoconfig.js in the Firefox installation’s defaults/pref directory and firefox.cfg at the top level of that installation. On macOS the base is Firefox.app/Contents/Resources. The generated loader uses LF endings and sets general.config.filename to firefox.cfg and general.config.obscure_value to 0 for plain text. Installation may require administrator permissions.
Obscured files
Firefox normally expects AutoConfig bytes shifted by 13 unless obscure_value is set to 0. The encoder adds 13 to each byte, not just alphabetic characters. If you encode firefox.cfg, change the loader to obscure_value 13. The decoder reverses that operation. This is compatibility obfuscation and offers no confidentiality.
Verify on the target version
Restart a test Firefox installation and inspect the relevant preferences in about:config. A preference can be renamed, removed or governed by enterprise policies. This generator does not check whether a preference exists. Consult Mozilla’s official AutoConfig documentation for deployment details.