|Part of |
|Networks and protocols|
|Development and societal aspects|
|Non-public file sharing|
|Websites and services|
|By country or region|
BitTorrent is one of the most common protocols for transferring large files, such as
To send or receive files, a person uses a
As of 2013, BitTorrent has 15–27 million concurrent users at any time.As of January 2012, BitTorrent is utilized by 150 million active users. Based on this figure, the total number of monthly BitTorrent users may be estimated to more than a quarter of a billion.
The BitTorrent protocol can be used to reduce the server and network impact of distributing large files. Rather than downloading a file from a single source server, the BitTorrent protocol allows users to join a "swarm" of hosts to upload to/download from each other simultaneously. The protocol is an alternative to the older single source, multiple mirror sources technique for distributing data, and can work effectively over networks with lower
The file being distributed is divided into
Pieces are typically downloaded non-sequentially and are rearranged into the correct order by the BitTorrent client, which monitors which pieces it needs, and which pieces it has and can upload to other peers. Pieces are of the same size throughout a single download (for example a 10 MB file may be transmitted as ten 1 MB pieces or as forty 256 KB pieces). Due to the nature of this approach, the download of any file can be halted at any time and be resumed at a later date, without the loss of previously downloaded information, which in turn makes BitTorrent particularly useful in the transfer of larger files. This also enables the client to seek out readily available pieces and download them immediately, rather than halting the download and waiting for the next (and possibly unavailable) piece in line, which typically reduces the overall time of the download. Once a peer has downloaded a file completely, it becomes an additional seed. This eventual transition from peers to seeders determines the overall "health" of the file (as determined by the number of times a file is available in its complete form).
The distributed nature of BitTorrent can lead to a
One such example of BitTorrent being used to reduce the distribution cost of file transmission is in the