Courts consider four factors when deciding whether a particular use is fair use or not:
- Purpose and character of the use. Nonprofit use is more likely to be fair use than use for commercial gain is. Transformative use is more likely to be fair use than non-transformative use is.
- Nature of the work. Use of a factual or nonfiction work is more likely to be fair use than use of a highly creative work (such as fiction) is.
- Amount and substantiality of the portion(s) used. Copying a small part of a work is more likely to be fair use than copying a lot of it is. Copying the heart of a work is less likely to be fair use than copying peripheral elements of a work is.
- Effect on the market for the work. The more a newly created work serves as a market substitute for the original, the less likely it is to be fair use. A work that competes in the same market against the original is not likely to be fair use. A work that does not compete in the same market with the original work (such as parody) is likely to be fair use.
None of these factors, standing alone, is determinative. In every case, courts must consider all four factors and decide how much weight to ascribe to each one relative to the other. Fair use analysis is very fact-dependent.