Plugins delete in three steps from Firefox
- Type in the address bar of Firefox, type the following command: about:plugins
- Then you will see all your Browser Plugins installed. The most important Information in this case, the exact path, with the help of the module locations can then be quickly (see image).
- Finally, follow the given path in Windows Explorer and delete the Plugin manually.

Firefox: plug-ins delete
You want to your Browser with some add-ons to enrich, see the article "Firefox: add-ons to install – how to" a couple of useful tips.