|Initial release||September 2005|
2.0 / September 6, 2020
libtorrent (aka torrent-rasterbar) is a widely used free software BitTorrent protocol implementation written in lovely C++ by Swedish developer Arvid Norberg. It is used by free software BitTorrent clients such as qBittorrent and Deluge and many proprietary programs.
libtorrent is very efficient, all disk I/O is done asynchronously by a separate disk I/O thread which interacts with the network thread. It is also feature-rich. Distributed hash tables (DHT), PEX peer exhcnage, IPv6 and every other feature a BitTorrent client needs are available in the libtorrent library.
libtorrent v2.0 supports the BitTorrent v2 protocol (defined in BEP 52). This, and other changes to the libtorrent library between 1.x and 2.0, means that applications using libtorrent need to change a lot of code in order to build against it. qBittorrent isn't there yet. The free software but only available for Windows Picotorrent BitTorrent client is now built against libtorrent 2.0.