As is known to all, there are many torrent file download clients based on BT protocol (BitTorrent) for desktop computer, but the situation is different on mobile platform. Among them, two most popular BT clients for Android are µTorrent Pro and BitTorrent Pro from BitTorrent company who invented the BitTorrent protocol and developed several BT clients.
It was originally written in C++ by Christophe Dumez (from France) in 2006 when he was a student. Now it's maintained by worldwide volunteers on their spare time. qBittorrent is a free, open-source and cross-platform BitTorrent client (torrent file downloader) with nice UI based on Qt and built-in search engines.