MGM Studios, Inc. v. Grokster, Ltd., 545 U.S. 913 (2005) is a unanimous Supreme Court decision with one holding: a distributor who markets a product with the object of promoting its use to infringe copyright, shown by clear expression or other affirmative steps taken to foster infringement, is liable for the infringement users commit with it. The Sony Betamax defense survived the case. It simply does not cover a company whose marketing, targeting, and business model prove an intent to cause piracy.
That rule now reaches far beyond 2005-era file sharing. Stream rippers, scraping tools, AI front ends, and leak utilities all sit somewhere on the line between capable of infringement and sold to infringe. Builders need to know where that line sits. Rightsholders need to know what evidence moves it.
The Grokster Facts: Free P2P Software and the Market Napster Left Behind
The original Napster went down in 2001, under injunctions that followed the Ninth Circuit's finding of contributory and vicarious liability. Millions of users needed a replacement, and two companies rushed to meet them. The lessons from the Napster shutdown matter here for one reason: Grokster's fate turned on what those companies did to capture that audience.
Grokster Ltd. distributed a free peer-to-peer client built on the FastTrack network; StreamCast Networks distributed Morpheus, a Gnutella client. Both were decentralized. No central index, no files on company servers, the opposite of Napster's choke point.
Revenue came from advertising. The clients were free, ads served during use, and income scaled with volume. The record showed the overwhelming majority of shared files were copyrighted works, and both companies knew it.
MGM and a coalition of studios, record labels, music publishers, and songwriters sued in the Central District of California for contributory and vicarious copyright infringement. In 2003 the district court granted the defendants summary judgment. The Ninth Circuit affirmed in 2004, reading Sony to bar liability for any product capable of substantial noninfringing use. The Supreme Court took the case and, on June 27, 2005, reversed unanimously.
The Sony Betamax Rule and Why It Wasn't Enough
In Sony Corp. v. Universal City Studios, 464 U.S. 417 (1984), the Court held that selling VCRs did not make Sony liable for customers taping copyrighted broadcasts. Time-shifting was fair use, and the staple-article-of-commerce doctrine, borrowed from patent law, barred liability for distributing a product with substantial noninfringing uses, even when the seller knows infringement is happening.
Both lower courts treated Sony as the end of the analysis. A product capable of substantial lawful use meant no liability, whatever the actual mix of use and whatever the companies knew.
Justice Souter's opinion for a unanimous Court rejected that reading. Sony answers a design question: what can the product do? It says nothing about a distributor who acts with the purpose of causing infringement. Patent law had always split secondary liability into contributory infringement, the staple-article rule Sony borrowed, and active inducement, codified at 35 U.S.C. § 271(b). Copyright law had only ever decided the first question. Grokster decided the second.
The Inducement Theory: Intent Proven by Conduct
The holding, verbatim: one who distributes a device with the object of promoting its use to infringe copyright, as shown by clear expression or other affirmative steps taken to foster infringement, is liable for the resulting acts of infringement by third parties.
Every phrase does work. "Object of promoting" makes intent the element, but intent is proven by conduct, not by the product's architecture. "Clear expression or other affirmative steps" reaches both explicit marketing and patterns of encouragement. "Resulting acts of infringement" requires actual third-party infringement; intent alone creates no liability. And the rule stacks on top of Sony rather than replacing it, so a tool with genuine lawful uses stays lawful to build and sell until its maker crosses into fostering.
Two limits matter just as much. Mere knowledge that infringement is occurring does not create inducement liability, the Court was explicit. And the rule is fact-intensive: marketing, business records, and internal communications get weighed together, which is why these disputes usually end with a jury or a settlement rather than a bright-line ruling.
The Evidence That Sank Grokster and StreamCast
The Court relied on three strands of evidence, and they remain the template for every inducement case since.
First, both companies targeted Napster's refugees. Grokster's name derived from Napster's. StreamCast's internal documents showed plans to capture the users Napster would lose, and the record included its operation of OpenNap servers, a Napster-compatible network, to meet those users before steering them to Morpheus.
Second, the business model. Free software, ad revenue, and no other meaningful income meant profits rose and fell with volume, and both companies knew what the volume was.
Third, deliberate inaction. The opinion notes that neither company attempted to develop filtering tools or any other mechanism to diminish infringement, even as copyright owners complained and litigation loomed. Encouragement on one side, studied indifference on the other.
No single strand would have carried the case. The combination did. That is the practical lesson: courts weigh the whole pattern of conduct, and in litigation the internal documents, emails, business plans, launch strategies, always surface.
Aftermath: Grokster's $50 Million Shutdown and LimeWire's $105 Million
The ruling took months to bite. In November 2005, Grokster settled: the service shut down and the company paid $50 million. StreamCast fought on, lost on remand, and ended in bankruptcy. Kazaa settled with the recording industry in 2006 for $100 million and relaunched with filtering and licensed content. The commercial P2P sector folded company by company, one chapter of the wider campaign traced in our history of RIAA piracy lawsuits.
LimeWire watched all of it and changed nothing. In Arista Records v. Lime Group, in the Southern District of New York, Judge Kimba Wood applied Grokster to a record that looked worse: marketing aimed at file sharers, in-app messaging that promoted infringing uses, an ad model tied to volume, no meaningful filtering, and founder Mark Gorton's own awareness of the core use. May 2010 brought summary judgment for the plaintiffs on inducement. October 2010 brought an injunction that shut the service down. A damages trial began in May 2011 and settled mid-trial for $105 million.
Two years later, the Justice Department shut Megaupload down with criminal charges, a different enforcement tool, different standards, much higher stakes. Read the Megaupload shutdown story for that branch of the timeline.
What MGM v. Grokster Did Not Decide
The opinion has careful limits, and all of them matter.
Sony stands. The Court said it need not revisit the Betamax rule because inducement resolved the case. The concurrences fought about how Sony applies, Justice Ginsburg, joined by Chief Justice Rehnquist and Justice Breyer, would have held that evidence of overwhelmingly infringing use could defeat summary judgment on its own; Justice Breyer, joined by Justices Stevens and O'Connor, thought Sony's threshold was satisfied, but no justice argued for overruling it.
No percentage threshold exists. The Court refused to say how much infringing use is too much, and litigants who ask for a simple ratio still do not get one.
The safe harbors were untouched. Grokster and StreamCast never relied on the § 512 safe harbor, the fight was over Sony and intent, not takedown compliance, and the ruling says nothing about hosts that do qualify.
And the hard middle cases went undecided. Mixed messaging, partial mitigation, tools with genuine dual uses: those still turn on their facts, which is exactly why they settle or go to juries.
If You Build a Tool Today: The Grokster Standard
Split the question in two. Your product's capability settles whether Sony protects the design. Your conduct settles whether you induced infringement. The second question is answered by public, discoverable material: marketing copy, onboarding screens, FAQ answers, ad placements, keyword buys, support replies, founder interviews, conference talks.
That yields a working posture for any tool that can infringe. Disavow infringement clearly and repeatedly. Document the lawful uses and keep them alive, Breyer's concurrence treated even a minority share of lawful use, at scale, as potentially substantial. If filtering or mitigation is feasible, make a considered decision and put the reasoning in writing. Make sure revenue is not a pure function of infringing volume.
The modern echoes are direct. Labels now run Grokster-style claims against stream rippers, and the stream-ripper lawsuits are the case's closest descendants. The wave of AI copyright lawsuits is testing whether marketing a model's ability to reproduce protected works counts as encouragement. The RIAA's takedown of youtube-dl on GitHub shows how much of this fight now happens through platform policy rather than courts: GitHub restored the repository after concluding the notice had serious problems, a policy outcome, not a ruling. If your users are in the EU, different rules apply again, since Article 17's upload filters impose platform obligations by statute rather than by intent.
If You Enforce Against a Tool Today: The Inducement Case
A takedown notice removes a copy. It does nothing to the distributor. Effective campaigns against tool makers run two tracks at once.
Track one is the copy problem. Notices to hosts, platforms, and search engines clear the infringing material, the mechanics are in our guide to filing a DMCA takedown notice, and the DIY takedown route works when budget is the constraint. Track two is the operator problem, and it needs an evidence file.
The file that moves these cases holds public marketing claims, ad targeting choices such as piracy-site placements and suspicious keyword buys, founder statements, the revenue model, and dated documentation of the operator's refusal to adopt available mitigation. Internal emails matter most, but they arrive only in discovery. Bank the public record first, with screenshots and archive captures.
Match the theory to the target. A platform that ignores notices is a § 512 fight, Viacom v. YouTube turned on knowledge and process, and BMG v. Cox showed that an ISP without a working repeat-infringer policy faces secondary liability. A tool whose maker promotes infringement is a Grokster fight, and Grokster fights end in eight-figure settlements once the intent evidence is visible.
Frequently Asked Questions About MGM v. Grokster
Did MGM v. Grokster Overrule Sony v. Universal?
No. All nine justices left the Betamax rule intact. Grokster added a separate ground of liability on top of it: a distributor who actively promotes infringement cannot claim Sony's substantial-noninfringing-uses protection. The concurrences disagreed over how Sony applies to mostly infringing products, but no justice argued the two rules cannot coexist.
What Is the Inducement Rule?
Under Grokster, a distributor is liable for third-party infringement when it distributes a device with the object of promoting infringing use, shown by clear expression or affirmative steps that foster infringement. Product design matters less than seller conduct. Mere knowledge that users infringe is not enough; encouragement plus resulting infringement is.
Why Did LimeWire Pay $105 Million?
In Arista Records v. Lime Group, Judge Kimba Wood found the Grokster pattern: marketing aimed at file sharers, ad revenue that scaled with infringement, and no filtering. Summary judgment for the labels came in May 2010, the injunction shut the service that October, and the damages trial settled mid-trial in May 2011 for $105 million.
Can a Tool With Substantial Legal Uses Still Get Its Maker Sued?
Yes. Sony protects products capable of substantial noninfringing use from design-based liability. Grokster makes the seller's intent a separate question. A tool with real lawful uses can still expose its maker if the maker markets infringement, targets infringing communities, and rejects reasonable mitigation. Those mixed cases go to juries, not motions.
What Evidence Proves Inducement?
Courts weigh marketing claims, onboarding and FAQ copy, ad targeting, founder statements, the revenue model, and whether the distributor adopted or rejected available mitigation. Internal emails and business plans carry the most weight but surface only in discovery. Start with the public record: archived pages, screenshots, and dated proof of what the operator said and refused to do.
What to do next
- Audit every public statement touching the tool, yours if you build, theirs if you enforce. That record decided Grokster.
- If you build, disavow infringement clearly, document lawful uses, and put mitigation decisions in writing.
- If you enforce, keep notices running against infringing copies while you build the intent file against the operator.
- Match theory to target: § 512 for platforms and hosts, inducement for tool makers.
- Get a professional read before the dispute hardens. Our guide to when to hire a copyright lawyer covers the decision points, and our published pricing is here if you would rather hand the enforcement work to a service.