I installed this addon on Firefox 54.0 64bit running on Linux Mint 18.1. My other addons are: Easy Youtube Downloader Express, Adblock Plus, and Javascript Switch. It works perfectly for disabling media content on news sites I visit, including HTML5 videos. The simple drop down menu is easy to use, and seems to remember specific site settings. It also does not interfere with videos on YouTube that I want to watch or download. Thank you, Tibor.