PUIDs (Portable Unique IDentifier) are the IDs used in the proprietary MusicDNS AudioFingerprinting system which is operated by MusicIP.

MusicBrainz server has started to use these IDs in March 2006 and have been implemented into Picard 0.7.0 released in July 2006.

There are currently many open questions regarding PUIDs, and the documentation is just being written up:

• HowPUIDsWork
• Several blogposts on the MusicBrainz Blog by RobertKaye:
  • March 12, 2006 New fingerprinting technology available now!
  • March 13, 2006 New fingerprinting questions answered
  • March 28, 2006 Picard: Common questions answered and
  • March 30, 2006 PUIDs: WTF?