BitTorrent (abbreviated to BT) is a communication protocol for peer-to-peer file sharing (P2P) which is used to distribute data and electronic files over the Internet.

BitTorrent is one of the most common protocols for transferring large files, such as digital video files containing TV shows or video clips or digital audio files containing songs. Peer-to-peer networks have been estimated to collectively account for approximately 43% to 70% of all Internet traffic (depending on location) as of February 2009.[1] In February 2013, BitTorrent was responsible for 3.35% of all worldwide bandwidth, more than half of the 6% of total bandwidth dedicated to file sharing.[2]

To send or receive files, a person uses a BitTorrent client on their Internet-connected computer. A BitTorrent client is a computer program that implements the BitTorrent protocol. Popular clients include μTorrent, Xunlei,[3] Transmission, qBittorrent, Vuze, Deluge, BitComet and Tixati. BitTorrent trackers provide a list of files available for transfer, and allow the client to find peer users known as seeds who may transfer the files.

Programmer Bram Cohen, a former University at Buffalo student,[4] designed the protocol in April 2001 and released the first available version on 2 July 2001,[5] and the most recent version in 2013.[6] BitTorrent clients are available for a variety of computing platforms and operating systems including an official client released by BitTorrent, Inc.

As of 2013, BitTorrent has 15–27 million concurrent users at any time.[7]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.[8]

Animation of protocol use: The colored dots beneath each computer in the animation represent different parts of the file being shared. By the time a copy to a destination computer of each of those parts completes, a copy to another destination computer of that part (or other parts) is already taking place between users.


The middle computer is acting as a "seed" to provide a file to the other computers which act as peers.

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 bandwidth. Using the BitTorrent protocol, several basic computers, such as home computers, can replace large servers while efficiently distributing files to many recipients. This lower bandwidth usage also helps prevent large spikes in internet traffic in a given area, keeping internet speeds higher for all users in general, regardless of whether or not they use the BitTorrent protocol. A user who wants to upload a file first creates a small torrent descriptor file that they distribute by conventional means (web, email, etc.). They then make the file itself available through a BitTorrent node acting as a seed. Those with the torrent descriptor file can give it to their own BitTorrent nodes, which—acting as peers or leechers—download it by connecting to the seed and/or other peers (see diagram on the right).

The file being distributed is divided into segments called pieces. As each peer receives a new piece of the file, it becomes a source (of that piece) for other peers, relieving the original seed from having to send that piece to every computer or user wishing a copy. With BitTorrent, the task of distributing the file is shared by those who want it; it is entirely possible for the seed to send only a single copy of the file itself and eventually distribute to an unlimited number of peers. Each piece is protected by a cryptographic hash contained in the torrent descriptor.[6] This ensures that any modification of the piece can be reliably detected, and thus prevents both accidental and malicious modifications of any of the pieces received at other nodes. If a node starts with an authentic copy of the torrent descriptor, it can verify the authenticity of the entire file it receives.

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 flood-like spreading of a file throughout many peer computer nodes. As more peers join the swarm, the likelihood of a completely successful download by any particular node increases. Relative to traditional Internet distribution schemes, this permits a significant reduction in the original distributor's hardware and bandwidth resource costs. Distributed downloading protocols in general provide redundancy against system problems, reduce dependence on the original distributor[9] and provide sources for the file which are generally transient and therefore harder to trace by those who would block distribution compared to the situation provided by limiting availability of the file to a fixed host machine (or even several).

One such example of BitTorrent being used to reduce the distribution cost of file transmission is in the BOINC client-server system. If a BOINC distributed computing application needs to be updated (or merely sent to a user), it can do so with little impact on the BOINC server.[10]

Other Languages
Afrikaans: BitTorrent
العربية: بت تورنت
asturianu: BitTorrent
azərbaycanca: Torrent
беларуская: BitTorrent
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bosanski: BitTorrent
català: BitTorrent
čeština: BitTorrent
Cymraeg: BitTorrent
dansk: BitTorrent
Deutsch: BitTorrent
eesti: BitTorrent
Ελληνικά: BitTorrent
español: BitTorrent
Esperanto: BitTorento
euskara: BitTorrent
français: BitTorrent
galego: BitTorrent
한국어: 비트토렌트
हिन्दी: बिट टॉरेंट
hrvatski: BitTorrent
Ilokano: BitTorrent
Bahasa Indonesia: BitTorrent
italiano: BitTorrent
עברית: ביטורנט
ქართული: BitTorrent
kurdî: BitTorrent
latviešu: BitTorrent
lietuvių: BitTorrent
magyar: BitTorrent
Bahasa Melayu: BitTorrent (protokol)
Nederlands: BitTorrent
日本語: BitTorrent
norsk: BitTorrent
norsk nynorsk: BitTorrent
polski: BitTorrent
português: BitTorrent
română: BitTorrent
Scots: BitTorrent
Simple English: BitTorrent
slovenčina: BitTorrent
slovenščina: BitTorrent
српски / srpski: BitTorrent
srpskohrvatski / српскохрватски: BitTorrent
suomi: BitTorrent
svenska: Bittorrent
татарча/tatarça: BitTorrent (протокол)
Türkçe: BitTorrent
українська: BitTorrent (протокол)
اردو: بٹ ٹورنٹ
Tiếng Việt: BitTorrent
粵語: BitTorrent