Fair Use in Copyright Law: The Four Factors Explained

Fair use is the most important — and most misunderstood — doctrine in U.S. copyright law. It permits limited use of copyrighted material without the owner's permission, and it is what makes commentary, criticism, news reporting, teaching, research, and parody possible. But "fair use" is not a checklist or a word count; it is a flexible, fact-specific defense that courts decide case by case under Section 107 of the Copyright Act (17 U.S.C. § 107).

The four fair-use factors

Section 107 directs courts to weigh four factors together — no single one is decisive:

• 1. The purpose and character of the use. Is it commercial or nonprofit and educational? And crucially, is it transformative — does it add new meaning, message, or purpose rather than merely substitute for the original?
• 2. The nature of the copyrighted work. Use of factual works is more likely fair than use of highly creative works; unpublished works receive stronger protection.
• 3. The amount and substantiality used. Using less favors fair use — but taking the "heart" of a work can weigh against it even if the portion is small.
• 4. The effect on the market for the original. Often the most important factor: does the use harm the copyright owner's actual or potential market, including licensing markets?

The transformative-use question

The Supreme Court made "transformativeness" central in Campbell v. Acuff-Rose Music (1994), holding that 2 Live Crew's parody of "Oh, Pretty Woman" could be fair use because parody comments on the original. In Google LLC v. Oracle America (2021), the Court found Google's reuse of Java API declarations to build a new platform was transformative and fair.

How Warhol narrowed it

The most important recent development is Andy Warhol Foundation v. Goldsmith (2023). The Court held that when a secondary use shares the same commercial purpose as the original (there, licensing an image of Prince to magazines), the first factor does not favor fair use simply because the new work adds some new expression. After Warhol, adding a new aesthetic is not automatically "transformative" — courts look hard at whether the use competes with the original's market.

What this means in practice

Fair use is a defense you raise after being accused of infringement, not a permission slip you grant yourself. Because it is fact-specific, the safest path is to use only what you need, add genuine commentary or transformation, and avoid uses that substitute for the original in its market. When the stakes are high, permission or a license is more predictable than betting on fair use. To see how fair use compares to a parallel doctrine in patent law, read doctrine of equivalents vs. fair use.