I don't think there is a built-in setting for that. The one used on desktop versions of Firefox has no effect in the Android version (browser.tabs.closeButtons). The easiest workaround I could find was the Quick Gestures extension. One of the many actions for which you can define a gesture is to close the current tab. By default, the gesture is Down Right Up, which didn't seem to work for me. I changed it to Left Right Left and that does work. If you haven't installed any add-on in Firefox for Android before: menu > Tools > Add-ons > Browse all Firefox add-ons Here you can search for gestures After installing, return to the tab with Add-ons, tap Quick Gestures and then tap Enable and under Preferences, Open. Then you can see and customize individual gestures.