uTorrent (or uTorrent and commonly abbreviated as "uT" or "uT") is a freeware closed source BitTorrent client by BitTorrent, Inc.. It is available for both Microsoft Windows and Mac OS X. Both versions are written in C++.[1] It gets the "u" in its name from the SI prefix "micro" meaning one one-millionth and it refers to the program's small footprint. The program is designed to use minimal computer resources while offering functionality comparable to larger BitTorrent clients such as Vuze or BitComet.