In an enterprise environment, it may be necessary to deploy Firefox with a set of predefined extensions. This can be done easily on the Firefox ESR build from the Firefox installation directory. These steps also work if you are customizing the Windows installer.

Step 1: Create directories

In the Firefox ESR installation directory, you will need to create some required directories. First, create a directory called distribution. Inside that directory, create another called extensions.

Step 2: Add extensions

We now need to add our extensions into the extensions directory that we created above. This will require you to know the add-on ID for each extension that you wish to add to this directory.

To add the extensions to this directory, you should include the extension's XPI file. It will need to be renamed to the add-on ID, while being careful to keep the .xpi file extension.

Alternatively, you can also create another directory in extensions named after the add-on ID. You can then unzip the extension into this directory.