Magnet is a

URI scheme A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...

that defines the format of magnet links, a

de facto standard A ''de facto'' standard is a custom or convention that has achieved a dominant position by public acceptance or market forces (for example, by early entrance to the market). is a Latin phrase (literally " in fact"), here meaning "in practice b ...

for identifying files (

URN An urn is a vase, often with a cover, with a typically narrowed neck above a rounded body and a footed pedestal. Describing a vessel as an "urn", as opposed to a vase or other terms, generally reflects its use rather than any particular shape or ...

) by their content, via cryptographic hash value rather than by their location. Although magnet links can be used in a number of contexts, they are particularly useful in

peer-to-peer file sharing Peer-to-peer file sharing is the distribution and sharing of digital media using peer-to-peer (P2P) networking technology. P2P file sharing allows users to access media files such as books, music, movies, and games using a P2P software program th ...

networks because they allow resources to be referred to without the need for a continuously available host, and can be generated by anyone who already has the file, without the need for a central authority to issue them. This makes them popular for use as "guaranteed" search terms within the

file sharing File sharing is the practice of distributing or providing access to digital media, such as computer programs, multimedia (audio, images and video), documents or electronic books. Common methods of storage, transmission and dispersion include r ...

community where anyone can distribute a magnet link to ensure that the resource retrieved by that link is the one intended, regardless of how it is retrieved.

History

The standard for Magnet URIs was developed by Bitzi in 2002, partly as a "vendor- and project-neutral generalization" of the ed2k: and freenet: URI schemes used by

eDonkey2000 eDonkey2000 (nicknamed "ed2k") was a peer-to-peer file sharing application developed by US company MetaMachine (Jed McCaleb and Sam Yagan), using the Multisource File Transfer Protocol. This client supports both the eDonkey2000 network and the ...

and

Freenet Freenet is a peer-to-peer platform for censorship-resistant, anonymous communication. It uses a decentralized distributed data store to keep and deliver information, and has a suite of free software for publishing and communicating on the Web ...

, respectively, and attempts to follow official

IETF The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...

URI standards as closely as possible. BitTorrent introduced the btmh: protocol in 2020 as part of its BitTorrent v2 changes.

Format

Magnet URIs consist of a series of one or more parameters, the order of which is not significant, formatted in the same way as

query string A query string is a part of a uniform resource locator (URL) that assigns values to specified parameters. A query string commonly includes fields added to a base URL by a Web browser or other client application, for example as part of an HTML, cho ...

s that ordinarily terminate

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide We ...

URLs. The following parameters are supported: The standard also allows for application-specific experimental parameters, which must begin with "x".

Exact Topic (xt)

The xt parameter specifies the URN for a given p2p protocol. Its purpose is to provide a search parameter for finding the metadata to the torrent. This effectively acts as a replacement to a .torrent file, which itself contains the torrent metadata, by instead searching the p2p network (using the URN) for that metadata. Each protocol handles a URN uniquely; for example, xt=urn:btih:FFC7E738EAA4CD4ECF51EC6FD669C6CDE2C281A8 uses the btih (BitTorrent v1 protocol), so a BitTorrent client can take the hash and lookup the torrent's metadata in the BitTorrent DHT. In the case of DHT the client searches through a set of pre-known nodes and requests the metadata for an infohash; those nodes will make the same request to other known nodes until eventually a swarm is found and returned. xt also allows for a group setting. Multiple files can be included by adding a count number preceded by a dot (".") to each link parameter. :

magnet:?xt.1=[ URN 


An urn is a  vase, often with a cover, with a typically narrowed neck above a rounded body and a footed pedestal. Describing a vessel as an "urn", as opposed to a vase or other terms, generally reflects its use rather than any particular shape or ...
 of the first file]&xt.2=[ URN of the second file]

; Merkle tree#Tiger tree hash, Tiger Tree Hash (TTH): These hashes are used on Direct Connect (file sharing), Direct Connect and Gnutella2, G2 (Gnutella2), among others. :

xt=urn:tree:tiger: TTH_ TTH_hash_sum">Hash_(Base32.html" ;"title="hash_sum.html" ;"title="Merkle_tree#Tiger_tree_hash.html" ;"title="Merkle tree#Tiger tree hash">TTH hash sum">Hash (Base32">hash_sum.html" ;"title="Merkle_tree#Tiger_tree_hash.html" ;"title="Merkle tree#Tiger tree hash">TTH hash sum">Hash (Base32) ]

; SHA-1, Secure Hash Algorithm 1 (SHA-1): These hash sums are used on

gnutella Gnutella is a peer-to-peer network protocol. Founded in 2000, it was the first decentralized peer-to-peer network of its kind, leading to other, later networks adopting the model. In June 2005, Gnutella's population was 1.81 million compute ...

and Gnutella2, G2 (Gnutella2). :

xt=urn:sha1: SHA-1_hash_function.html" ;"title="SHA-1.html" ;"title="SHA-1">SHA-1 hash function">Hash (Base32 

Base32 is the  base-32 numeral system. It uses a set of 32  digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper- ...
) ]

; BitPrint: Such hash sums consist of an SHA-1 Hash, followed by a TTH Hash, delimited by a point; they are used on

and Gnutella2, G2 (Gnutella2). :

xt=urn:bitprint: SHA-1_hash_function.html" ;"title="SHA-1.html" ;"title="SHA-1">SHA-1 hash function">Hash (Base32 

Base32 is the  base-32 numeral system. It uses a set of 32  digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper- ...
) ]. TTH_ TTH_hash_sum">Hash_(Base32.html" ;"title="hash_sum.html" ;"title="Merkle_tree#Tiger_tree_hash.html" ;"title="Merkle tree#Tiger tree hash">TTH hash sum">Hash (Base32">hash_sum.html" ;"title="Merkle_tree#Tiger_tree_hash.html" ;"title="Merkle tree#Tiger tree hash">TTH hash sum">Hash (Base32) ]

; EDonkey network#Hash identification, ED2K (eDonkey2000) hash: These hash sums are used on

. :xt=urn:ed2k:[ EDonkey network#Hash identification, ED2K hash sum, Hash ( Hex) ] ; AICH, Advanced Intelligent Corruption Handler (AICH): Not formal URNs for Magnet links, such hash sums are used by

to restore and control the integrity of downloading and already downloaded files. :

xt=urn:aich: AICH, aich  hash sum, Hash (Base32 

Base32 is the  base-32 numeral system. It uses a set of 32  digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper- ...
) ]

; Kazaa hash: Used on FastTrack, these hash sums are vulnerable to hash collision attacks. :xt=urn:kzhash:[ Kazaa hash sum, Hash ( Hex) ] ; BitTorrent info hash (BTIH): These are hex-encoded

SHA-1 In cryptography, SHA-1 (Secure Hash Algorithm 1) is a cryptographically broken but still widely used hash function which takes an input and produces a 160-bit (20- byte) hash value known as a message digest – typically rendered as 40 hexadec ...

hash sums of the "info" sections of BitTorrent metafiles as used by BitTorrent to identify downloadable files or sets of files. For backwards compatibility with existing links, clients should also support the

Base32 Base32 is the base-32 numeral system. It uses a set of 32 digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper- ...

encoded version of the hash. :

xt=urn:btih: BitTorrent_Info__BitTorrent Info  Hash.html" ;"title="hash sum, Hash">hash sum, Hash ( Hex) /code>
: Some clients require Base32 

Base32 is the  base-32 numeral system. It uses a set of 32  digits, each of which can be represented by 5 bits (25). One way to represent Base32 numbers in a human-readable way is by using a standard 32-character set, such as the twenty-two upper- ...
 of info_hash (e.g., Vuze 


Vuze (previously Azureus) is a BitTorrent client used to transfer files via the  BitTorrent protocol. Vuze is written in Java, and uses the Azureus Engine. In addition to downloading data linked to  .torrent files, Azureus allows users to view, p ...
).
; BitTorrent info hash v2 (BTMH):  BitTorrent v2 replaces the  obsolete SHA-1 hash with a SHA-256 


SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the  Merkle–Damgård construction, from a  one-way compressi ...
 info hash. The v2 info-hash is given a new prefix (btmh) to allow for torrents that can participate in both v1 and v2 swarms
:xt=urn:btmh: BitTorrent_Info__BitTorrent Info  Hash.html" ;"title="hash sum, Hash">hash sum, Hash ( Hex) /code>
;  Message Digest 5 (MD5): Supported by  Gnutella2, G2 (Gnutella2), such hashes are vulnerable to  hash collision attacks.
:xt=urn:md5: MD5__MD5  Hash.html" ;"title="hash sum, Hash">hash sum, Hash ( Hex) /code>

  Web links to the file 

There are two types of download links that a Magnet link can include as a direct or backup source.

; "as" ("acceptable source"): Most clients treat "as" as equal to the "xs" token when it comes to priority, and ignore the timeout before contacting "as" sources denoted by the specs.
; Content-Addressable Web URL: This type of -based link is used by gnutella 





Gnutella is a  peer-to-peer network protocol. Founded in 2000, it was the first decentralized peer-to-peer network of its kind, leading to other, later networks adopting the model.
 
In June 2005, Gnutella's population was 1.81 million compute ...
 as well as  Gnutella2, G2 applications.
:xs=http:// lient Address ort of clienturi-res/N2R? URN_


An_urn_is_a__vase,_often_with_a_cover,_with_a_typically_narrowed_neck_above_a_rounded_body_and_a_footed_pedestal._Describing_a_vessel_as_an_"urn",_as_opposed_to_a_vase_or_other_terms,_generally_reflects_its_use_rather_than_any_particular_shape_or_...

History

Format

Exact Topic (xt)

Web links to the file

Supplement format (x.)

Clients

See also

Explanatory notes

References

External links