User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Firefox/31.0 Build ID: 20140716183446 Steps to reproduce: I started to download 5 big files (a few GB each). Actual results: Firefox attempted to download them all simultaneously. I went to sleep and left it to download the files overnight. In the morning all the downloads failed, though network was working normally. I assume they failed because of the congestion caused by downloading all of them in parallel. This never happens with true download managers (like the Free Download Manager app). Expected results: Firefox should queue big files and download them one at a time. It can download smaller files in parallel with them (but limited to say 4 short files at a time) so that you don't wait forever on a small file while downloading big files. The threshold separating "small" from "big" files should be configurable (say 50 MB). But one should be able to manually override this during download. By right-clicking on a file and choosing "allow parallel download" or "queue for serial download". For example, when downloading small files from a very slow server, or over a congested network, serial download would be preferable. This would also help productivity. A user would get one big file at a time, so he can start working on it while the next one is downloading. Instead of sitting idle and waiting for ALL of them to finish simultaneously, and then get a ton of work in the same minute. Queuing would also solve the problem with more than 8 downloads from the same server. The small files that hit the server limit would just be queued and started later. Who needs 2000 downloads running in parallel anyway? I would have no need to install Free Download Manager if Firefox had the ability to queue files.