To prove copyright infringement, you have to establish two things by a preponderance of the evidence: that you own a valid copyright in the work, and that the defendant copied protected elements of it. Copying is almost never proved by a confession, so in practice you show it circumstantially — by proving the defendant had access to your work and that the two works are substantially similar. Before any of that matters, though, you generally have to register the work with the U.S. Copyright Office, because registration is what gets you into federal court and what determines the damages available if you win.
Register Before You Sue
Federal law bars an infringement suit involving a U.S. work until the Copyright Office has actually examined and registered the claim.1Office of the Law Revision Counsel. 17 U.S. Code 411 – Registration and Civil Infringement Actions Filing an application is not enough; the Supreme Court confirmed in 2019 that registration “has been made” only once the Register of Copyrights approves it.
There is a narrow exception. If the Copyright Office refuses your registration, you can still sue, provided you serve notice of the lawsuit on the Register along with a copy of the complaint. The Register then has sixty days to intervene on the registrability question.1Office of the Law Revision Counsel. 17 U.S. Code 411 – Registration and Civil Infringement Actions
Because processing can take several months, waiting until you discover infringement to register is risky. The delay eats into your three-year limitations window and can lock you out of the more valuable damage categories entirely.
Prove You Own a Valid Copyright
The first element splits into two questions: is the work the kind of thing copyright protects, and are you the person who owns the rights?
Copyright protects original works of authorship fixed in a tangible medium of expression.2Office of the Law Revision Counsel. 17 U.S. Code 102 – Subject Matter of Copyright: In General Originality is a low bar — you created it yourself with some minimal spark of creativity. Fixation means the work exists in a stable form someone can perceive: text on a page, a saved audio file, paint on canvas. An improvised melody at a party that no one recorded is not fixed and cannot be protected.
A registration certificate is the strongest proof of both validity and ownership. When registration happens before or within five years of the work’s first publication, the certificate is presumptive evidence that the copyright is valid and that the facts stated on it are accurate.3Office of the Law Revision Counsel. 17 U.S. Code 410 – Registration of Claim and Issuance of Certificate That presumption shifts the practical burden onto the defendant to come forward with contrary evidence.
Without a timely registration, you can still prove ownership through dated drafts, file metadata, development emails, and any contracts transferring rights to you. These are workable but slower and more expensive to establish than what a certificate does automatically.
Why Registration Timing Shapes Everything
Registration doesn’t just open the courthouse. It also decides which remedies you can pursue. Statutory damages and attorney’s fees are available only if you registered before the infringement began, or within three months of the work’s first publication.4Office of the Law Revision Counsel. 17 U.S. Code 412 – Registration as Prerequisite to Certain Remedies for Infringement Miss that window and you are limited to actual damages and the infringer’s profits, both of which are harder to prove and often smaller.
This is the trap most creators fall into. They discover copying, rush to register, and only then learn the infringement started months earlier. Statutory damages, which can reach $150,000 per work for willful infringement, are off the table at that point. Register important works promptly on creation or publication, before anyone infringes them.
Prove the Defendant Copied Your Work
Ownership alone wins nothing. The second element is that the defendant actually copied your protected expression. Independent creation is not infringement — if two people write similar songs without either hearing the other’s, neither has done anything wrong. The whole question is whether the defendant’s work derives from yours.
Direct evidence of copying, such as an admission by the infringer or a witness who saw it happen, is decisive but rare. Courts therefore allow copying to be shown circumstantially by proving two things together: that the defendant had access to your work, and that the two works are substantially similar. If you can prove both, the court can infer copying.
Showing Access
Access means the defendant had a reasonable opportunity to encounter your work before creating theirs. You do not have to prove they definitely saw or heard it, only that they realistically could have.5Ninth Circuit District and Bankruptcy Courts. 17.18 Copyright Infringement – Copying – Access Defined A bare theoretical possibility isn’t enough; there has to be a plausible path.
One route is a chain of events linking the two. If you submitted a screenplay to a production company and the defendant worked there as a development executive, a court can infer access. The same reasoning applies if you pitched a song to a label that later released a similar track by another artist on its roster.
The other route is wide public dissemination. A photograph on a heavily trafficked site, a song with significant radio play, a book sold through major retailers — all make it easier to argue the defendant could have encountered the work. The broader the distribution, the stronger the inference.
In rare cases the works are so alike that copying is the only plausible explanation, even without solid access proof. Courts call this “striking similarity,” a resemblance so specific and extensive that coincidence, independent creation, and a shared source are all ruled out.6Ninth Circuit District and Bankruptcy Courts. 17.17 Copying – Access and Substantial Similarity Where a plaintiff can meet this standard, a court may presume copying. Ordinary similarity does not trigger it.
Showing Substantial Similarity
Access proves opportunity. Substantial similarity proves that what the defendant took was enough to matter. This is usually the most contested part of an infringement case. The question isn’t whether the two works share some similarities; almost any two works in the same genre will. The question is whether the defendant took a significant amount of your protected creative expression.
Most courts frame the analysis around an “ordinary observer”: would a reasonable person recognize that one work was taken from the other?7Ninth Circuit District and Bankruptcy Courts. 17.19 Substantial Similarity – Extrinsic Test; Intrinsic Test The specific framework varies by circuit, but every version ultimately asks whether the taking crossed the line from ordinary resemblance into appropriation.
Running through the entire analysis is a critical limit: copyright protects expression, not ideas. The statute is explicit that protection does not extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery.2Office of the Law Revision Counsel. 17 U.S. Code 102 – Subject Matter of Copyright: In General The general premise of a wizarding school is available to any writer. The specific characters, storylines, and language used to render that premise are not.
That distinction drives what courts actually compare. Two novels can share the same premise — a hard-drinking detective in a small Southern town — without one infringing the other. Infringement enters when specific details start to match: the same unusual plot turns, the same distinctive character traits, the same sequence of events. Courts look at the “total concept and feel” of the works and filter out unprotectable material like stock characters and scenes that flow naturally from the premise before comparing what’s left. For music, that comparison focuses on melody, harmonic progression, and rhythm; for novels, on plot structure, character, and setting; for visual art, on composition, color, and arrangement.
Defenses You Should Expect
Two defenses come up in nearly every case, and preparing for them shapes your evidence.
The first is independent creation. Copyright, unlike patent, does not protect against parallel creation. If the defendant can convince the court they arrived at their work without any exposure to yours, they win. This is why strong access evidence matters so much: it forecloses the coincidence story before it starts.
The second is fair use, which permits unauthorized use for purposes like criticism, commentary, news reporting, teaching, or research. Courts weigh four factors:8Office of the Law Revision Counsel. 17 U.S. Code 107 – Limitations on Exclusive Rights: Fair Use
- The purpose and character of the use, including whether it is commercial or transformative.
- The nature of the copyrighted work, with factual works easier to use fairly than highly creative ones.
- The amount and substantiality of what was taken, keeping in mind that even a small portion can be too much if it captures the heart of the work.
- The effect on the market for or value of the original.
No single factor decides the question, and the defendant bears the burden of proving the defense applies. If you anticipate fair use, be ready to argue the use was not transformative, took too much, or damaged your market.
The Deadline to Sue
You have three years from the date the claim accrues to file suit.9Office of the Law Revision Counsel. 17 U.S. Code 507 – Limitations on Actions Miss it and the case is dismissed no matter how strong the underlying evidence.
Many federal circuits apply a discovery rule, starting the clock when you discovered or reasonably should have discovered the infringement rather than when it occurred. In 2024, in Warner Chappell Music, Inc. v. Nealy, the Supreme Court held that when a claim is timely under the discovery rule, the copyright owner can recover damages for the full period of infringement, even for copying that began more than three years before suit.10Supreme Court of the United States. Warner Chappell Music, Inc. v. Nealy (2024) The Court did not decide whether the discovery rule itself is correct, so that question remains open.
What You Can Recover
A successful plaintiff can seek several categories of relief. Which ones are actually on the table depends on when you registered.
Every prevailing plaintiff can recover actual damages, meaning the real financial harm from the infringement. The most common measure is the licensing fee the infringer should have paid: if you normally charge $2,000 for a photograph license and someone used it without paying, that is your actual damages.11U.S. Copyright Office. Copyright Claims Board Handbook – Damages Lost sales, lost licensing opportunities, and diminished market value can also count.
On top of that, you can claim the infringer’s profits from the infringement to the extent they are not already reflected in your actual damages. You only have to prove the infringer’s gross revenue from the infringing activity. The infringer then bears the burden of proving deductible expenses and revenue attributable to factors other than the copying.11U.S. Copyright Office. Copyright Claims Board Handbook – Damages
If your registration was timely, you can elect statutory damages instead of proving actual losses, at any time before final judgment. Statutory damages run from $750 to $30,000 per work infringed, as the court considers just. For willful infringement the ceiling rises to $150,000 per work. If the infringer convinces the court they had no reason to believe their conduct was infringing, the floor drops to $200.12Office of the Law Revision Counsel. 17 U.S. Code 504 – Remedies for Infringement: Damages and Profits Statutory damages are usually the more practical choice for smaller creators because they avoid the cost and uncertainty of documenting every dollar of harm.
Courts can also issue injunctions ordering the defendant to stop the infringing activity, either temporarily while the case proceeds or permanently after trial.13Office of the Law Revision Counsel. 17 U.S. Code 502 – Remedies for Infringement: Injunctions For many creators, stopping the ongoing use matters as much as the money.
Attorney’s fees are available at the court’s discretion to the prevailing party, but only if registration met the same timing requirements that govern statutory damages.14Office of the Law Revision Counsel. 17 U.S. Code 505 – Remedies for Infringement: Costs and Attorneys Fees Because copyright litigation runs into tens of thousands of dollars quickly, that possibility often decides whether a case is worth bringing at all.