Have you tried swiping it off of the recent applications panel? I don't know what that looks like in Android 7 but I suspect similar to Android 6. You also can add a Quit item to Firefox's menu if you set at least one category of data to be cleared when you quit Firefox. For example, you could select cached files. menu > Settings > Privacy > Clear private data on exit Avoid clearing "Site settings", which stores individual site permissions, and any other categories of data you aren't sure you can do without.