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Created page with "This page is also available in other languages: [https://zh.lolipedia.org/BT协议中文] == Overview == Master, the '''BitTorrent (BT) protocol''' is a peer-to-peer (P2P) file-distribution method: it avoids the “everyone crowding the same server” problem. Every downloader is also an uploader—downloading while uploading—and the more participants there are, the faster it gets. BT’s pioneering spirit of sharing is essential: in a BT swarm, seeders contribute mo..."

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This page is also available in other languages: [https://zh.lolipedia.org/BT协议中文]

== Overview ==
Master, the '''BitTorrent (BT) protocol''' is a peer-to-peer (P2P) file-distribution method: it avoids the “everyone crowding the same server” problem. Every downloader is also an uploader—downloading while uploading—and the more participants there are, the faster it gets. BT’s pioneering spirit of sharing is essential: in a BT swarm, seeders contribute more upload bandwidth to give downloaders faster speeds, and once downloaders finish, they can seed to become sharers themselves. <br>
BT accelerates the distribution of many kinds of content on the internet, especially large and popular files where BT offers excellent throughput. However, over time, large-scale “leeching” emerged—clients that download without contributing uploads—which undermines the BT ecosystem (e.g., the Chinese platform Xunlei/Thunder).

== Key Terms at a Glance ==
{| class="wikitable"
! Term !! Technical Definition
|-
| InfoHash v1/v2 || v1: SHA-1(info); v2: SHA-256(info with a Merkle file tree and piece layers).
|-
| DHT || Kademlia-style routing—i.e., a decentralized network—storing/fetching peers by XOR distance, over UDP.
|-
| PEX || An extension where peers in the same swarm exchange incremental peer lists.
|-
| uTP || A UDP-based transport with LEDBAT congestion control, reducing bandwidth contention with TCP.
|-
| MSE/PE || Link encryption to evade throttling/identification; **not** an anonymity tool.
|-
| WebSeed || Provides an HTTP source for the same content; the client fetches pieces in parallel with P2P.
|}

== The State of BT ==
BT torrents show a polarized trend: the vast majority become dead torrents due to a lack of seeders, or suffer poor efficiency because there are too few. Meanwhile, many popular sites (e.g., The Pirate Bay) have torrents with abundant seeders; for many hot releases—new films and popular pirated games—BT is widely used and often much faster than file-hosting services. <br>
Because BT itself does not solve copyright issues, pirated films, games, and software are freely distributed on the internet; consequently, many countries introduced laws to prohibit or restrict such use—for example, the U.S. Digital Millennium Copyright Act (DMCA). <br>
Because the BT protocol cannot fundamentally prevent leeching and sharing relies on users’ self-discipline, many individuals download far more than they upload—or don’t upload at all—severely damaging the BT ecosystem. Later, the PT model (private trackers) emerged as a smaller, gated community approach to mitigate leeching. <br>

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