Originally Posted by bsl

which version number should I use?

utorrent 1.8.1 and 2.2.1 most used versions but 2.2.1 have problem with https trackers, 1.8.1 dont have udp tracker support also udp tracker support is not important if you dont use public tracker. For utorrent a lot of tracker recommend 2.2.1 but first they recommend qbittorrent which is best right now according to almost every private tracker. so if you can, use qbittorrent if you dont want to and you want to use utorrent than use 2.2.1