BitTorrent is a protocol that underpins the practice of peer-to-peer file sharing and is used for distributing large amounts of data over the Internet. BitTorrent is one of the most common protocols for transferring large files and it has been estimated that, collectively, peer-to-peer networks have accounted for approximately 43% to 70% of all Internet traffic (depending on geographical location) as of February 2009. Most of this peer-to-peer traffic is likely from BitTorrent, after the demise of LimeWire.

Programmer Bram Cohen designed the protocol in April 2001 and released the first available version on July 2, 2001. Currently, numerous BitTorrent clients are available for a variety of computing platforms, including an official one released by Bittorrent, Inc.

As of January 2012, BitTorrent is utilized by 150 million active users (according to BitTorrent, Inc.). Based on this figure, the total number of monthly BitTorrent users can be estimated at more than a quarter of a billion. At any given instant, BitTorrent has, on average, more active users than YouTube and Facebook combined (this refers to the number of active users at any instant and not to the total number of unique users). Since 2010, more than 200,000 users of the protocol have been sued by copyright trolls.

Read more about BitTorrent:  Description, Operation, Adoption, Indexing, Technologies Built On BitTorrent, Implementations, Development, Legal Issues, BitTorrent and Malware