Refiling this from here: https://github.com/mozilla/multi-account-containers/issues/861 My win10 desktop has two monitors: A 4k monitor at 225% scaling A non-4k monitor at 125% scaling Trying to use the extension container drawer menu on the second monitor is difficult. The scaling is not properly detected. The attached screenshot is what it looks like in FF57 beta. It looks correct in windows on the primary monitor. This problem affects both the containers addon and ublock origin.