DownThemAll! is a download manager/accelerator built as an Addon in Mozilla Firefox. Currenty, DownThemAll! is not compatible with Firefox Quantum. You will get the following message when visiting DownThemAll! webpage: This add-on is not compatible with your version of Firefox. One alternative for DownThemAll! is uGet. uGet is an Open Source and multi-platform download manager. It works in Linux, BSD, Android and Windows. uGet is a stand-alone application but you can install a Firefox Addon to replace Firefox’s default download…