What is "metalink"

Metalink is an extensible metadata file format that describes one or more computer files available for download. It specifies files appropriate for the user's language and operating system; facilitates file verification and recovery from data corruption; and lists alternate download sources ( mirror URIs).

The metadata is encoded in HTTP header fields and/or in an XML file with extension .meta4 or .metalink. The duplicate download locations provide reliability in case one method fails. Some clients also achieve faster download speeds by allowing different chunks/segments of each file to be downloaded from multiple resources at the same time ( segmented downloading).

Metalink supports listing multiple partial and full file hashes along with PGP signatures. Most clients only support verifying MD5, SHA-1, and SHA-256, however. Besides FTP and HTTP mirror locations and rsync, it also supports listing the P2P methods BitTorrent, ed2k, magnet link or any other that uses a URI.