Convert CRX to XPI

Unfortunately, converting browser extensions/plugins/add-ons from one web browser to another is difficult, for example, from Chrome (.crx) to Firefox (.xpi). Nevertheless, tools like the crx-to-xpi can port the crx version of some WebExtensions add-on to the XPI format. WebExtensions are a cross-browser system for developing browser add-ons. To a large extent, the system is compatible with the extension API supported by Google Chrome. Extensions written for this browser will, in most cases, run in Firefox with just a few changes.

When you want to port Google Chrome extensions to Firefox, the best choice is probably the ExtensionWorkshop website, where you get help creating and publishing Firefox add-ons and finding resources you need to start with extension development.