---
title: "Fair use"
description: "The US copyright defence that weighs four factors: purpose and transformativeness, nature of the work, amount used and market effect."
canonical: https://aigovernanceengineer.com/glossary/fair-use
author: "Jorge García Aibar"
license: "CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)"
doi: https://doi.org/10.5281/zenodo.22956197
version: "0.5.0"
updated: 2026-09-24
---

# Fair use

The US copyright defence that weighs four factors: purpose and transformativeness, nature of the work, amount used and market effect [1]. Courts apply it to AI training case by case; results so far turn on how the data was acquired and on each record.

- Developed in: [ch. 20, US training cases, dated](https://aigovernanceengineer.com/bok/existing-law#us-training-cases-dated)
- Chapters: [ch. 20, Existing Law](https://aigovernanceengineer.com/bok/existing-law)
- Contrast with: [TDM exception](https://aigovernanceengineer.com/glossary/tdm-exception)
- In the glossary chapter: https://aigovernanceengineer.com/bok/glossary#t-fair-use

## Sources

[1] 17 U.S.C. § 107, Limitations on exclusive rights: fair use (the four factors). Legal Information Institute, Cornell Law School. 2026. https://www.law.cornell.edu/uscode/text/17/107 (verified: secondary)