This add-on deactivates all plugins when Firefox starts. It is useful when you occassionally use a plugin which cannot be used if set to Ask to Activate yet you do not always want to set to Always Activate. In that case, this add-on deactivates the plugin after using it by disabling it the next time you start Firefox. An example of a plugin that cannot be used if set to Ask to Activate is the Gnome Shell Integration plugin (https://extensions.gnome.org/about/
Note: Plugin Disabler 0.2 does not deactivate the OpenH264 Video Codec plugin.