Ed2k URI scheme

In computing, eD2k links (ed2k://) are hyperlinks used to denote files stored on computers connected to the eDonkey filesharing P2P network.

Many programs, such as eMule, MLDonkey and the original eDonkey2000 client by MetaMachine, which introduced the link type, as well as others using the eDonkey file sharing protocol, can be used to manage files stored in the filesharing network.

eD2k links allow a file to be identified from a link in a web browser and to be downloaded thereafter by a client like eMule, Shareaza or any other compatible software. This linking feature was one of the first URIs to be introduced in peer-to-peer file sharing, and had a vast effect on the development of the eDonkey network, as it allowed external link sites to provide verified content within the network. Nowadays, so-called Magnet links have replaced eD2k links in practice. They serve a similar role, but are not limited to the eD2k hash and can contain other hashes such as SHA-1 or MD5 for example, which makes it possible to use these links to point to files in several networks (as well as in BitTorrent) at once.

eD2k links include file hashes, as these hashes can be used as a unique identifier for files within the network, so even if the linked-to file has a different name on two computers within the network, the file can be found on both of them, and file chunks can be obtained from both sources. This is done by using a hash function on the file to calculate its checksum, depending only from the file content, not from its name.

Like other URI protocols, web browsers can be configured to automatically handle ed2k URIs. After installing an eD2k client, the eD2k protocol is optionally registered so that clicking on it in the browser automatically starts the download or asks whether the user wants to start downloading.

...
Wikipedia