The lawsuits
The Napster lawsuit was a set of United States copyright cases brought against Napster, Inc. between 1999 and 2001 over file sharing, and they turned on one fact about how the program was built: the company operated the search index itself, so it knew what was on its network and had the means to filter it.
Nothing in the rulings concerned the transfers, which went directly between two people's computers and never touched the company. The reasoning ran on the index alone, and that is why the cases matter far beyond one defunct program. Every peer to peer design that came afterward was drawn by people who had read what happened to the part in the middle.
Which cases were actually filed
The cases filed against Napster came from three directions in under a year. The record industry moved first, in December 1999, when the Recording Industry Association of America brought suit for member labels in the United States District Court for the Northern District of California, in the action generally cited as A&M Records, Inc. v. Napster, Inc. The band Metallica filed separately in April 2000, and the producer and artist Dr. Dre brought a further suit the same year. The claims were not that Napster copied anything itself, but that the company was liable for the copying its users did, under the American doctrines of contributory and vicarious infringement.
Copyright law differs by country and by case, and this page describes what these particular American courts reasoned rather than what any rule is anywhere. Nothing on this page is advice to any reader.
What the courts decided, and what the decision turned on
The decision turned on knowledge and control, and Napster's architecture supplied both. Because the program uploaded each user's file list to Napster's own servers, the company held, at any moment, a list of the specific files available on its network. That is actual knowledge of specific material rather than a general awareness that some users somewhere misbehave. Because the servers were the company's, it also had the practical ability to supervise the system, and it had a financial interest in the traffic. In February 2001 the United States Court of Appeals for the Ninth Circuit largely upheld the district court's analysis and sent the matter back for an injunction drawn more narrowly.
The defense that failed is the interesting half. In 1984, in Sony Corp. of America v. Universal City Studios, the United States Supreme Court had held that selling a device capable of substantial uses that do not infringe is not itself contributory infringement, which is why a video recorder was lawful to sell. Napster argued the same shelter. The appeal court distinguished it on the ground that a manufacturer's relationship with a recorder ends at the till, while Napster's relationship with its index was continuous: it kept running the thing and could act on it.
Metallica and Napster
Metallica versus Napster was the same legal argument carried by a band rather than a label, and it became the public face of the dispute for reasons of personality rather than law. The band's suit followed the circulation of a work in progress recording before its release, and the band pursued the point that the network made its catalog available without permission. Metallica compiled a list of user names it wanted removed and delivered it to the company, and Napster disabled the accounts named on it, which demonstrated in public exactly the capability the labels were arguing about in court: the company could act on its own index whenever it chose to.
The cost to the band was reputational and the argument split its audience, a strand covered in the documentary Downloaded, directed by Alex Winter and released in 2013. For the technical history the significance is smaller than the noise around it: the band's case rested on the same index the labels' case rested on, and it would have failed against a network with no index to point at.
The cases that followed, and what each one turned on
The cases that followed Napster tested the same question against networks built differently, and the answers tracked the architecture closely.
| Case | Where and when | What it turned on |
|---|---|---|
| A&M Records, Inc. v. Napster, Inc. | United States, filed 1999, appeal decided 2001 | a central index the company ran, knew the contents of, and could police |
| Metallica v. Napster, Inc. | United States, filed 2000 | the same index, with the company shown acting on a list of names |
| The Kazaa proceedings | Netherlands, decided 2003 | software that worked without any server the maker operated |
| MGM Studios, Inc. v. Grokster, Ltd. | United States Supreme Court, 2005 | what the distributor encouraged, rather than what the software could do |
| Arista Records LLC v. Lime Group LLC | United States, decided 2010 | the same encouragement test applied to a widely used Gnutella client |
The Dutch proceedings against the makers of Kazaa produced the clearest contrast. By the time the case was decided in 2003 the software ran on a network of supernodes formed out of ordinary users' machines, so the company had no server to filter and no switch to throw, and the highest Dutch court declined to hold it responsible for a program it had merely written. Two years later the Grokster decision closed the gap from the other side: a distributor that promotes a tool as a means of infringement is liable for the infringement that follows, whatever the tool is capable of. That inducement reasoning later ended LimeWire, a long running Gnutella client, in 2010.
Why every design after Napster removed the switchable part
Every design after Napster removed the switchable part because the rulings had described precisely which part that was. eDonkey put the index on servers that stored no content and could be replaced by anybody, then eMule added the Kad table so that no server was required at all. BitTorrent kept no network wide index in the protocol whatsoever, coordinating one temporary swarm per file, and within a few years made even that coordination optional through distributed hash tables and magnet links. Syncthing shows the same instinct applied to private use, with no shared index existing anywhere.
None of that was a legal cure, as Grokster and the LimeWire case both showed, since conduct and encouragement are judged separately from architecture. It was an engineering response to a demonstrated failure mode. The Napster case did not prove that peer to peer file sharing was unlawful. It proved that a company running the middle of a network is a company that can be ordered to stop, and the field spent the next decade making sure there was no middle to run.