Magnet URI extension - Select specific file indices for download

Abstract

This magnet extension introduces the concept of an optional select-only file index array in the magnet URI, so that torrent clients can automatically select specific file(s) for download after the metadata has been downloaded.

Rationale

This extension would allow clients to know which specific file(s) within a torrent they should download, before the metadata has been downloaded. In particular it would allow for creating "deep links" to a specific file, folder, or subset of files within a torrent. A server could then host a magnet link, referring to that specific file or subset of files they wish to serve. This would be particularly useful for library torrents.

This extension would add an optional array of file indices to the magnet link.

URI extension

The new URI format would contain the following:

magnet:?xt=urn:btih:HASH&dn=NAME&tr=TRACKER&so=0,2,4,6-8

so=0,2,4,6-8 means select only, and the numbers are the file indices. Files are zero-indexed. Dashes mean inclusive ranges, so 6,7, and 8 are also added.

Special case: What if the magnet link is already added?

Torrent clients that already have added that torrent should add any currently not-downloading file indices, and set their priority to normal.

References

Copyright

This document has been placed in the public domain.

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