How much of a copyrighted material can be used under fair use?
Fair use is a defense to copyright infringement; it essentially makes allowable some instances of copyright infringement, such as educational purposes or parody.
What makes fair use difficult is that there is no brightline test or rule to apply in all instances; it varies on a case-by-case basis. There are 4 main factors that courts examine for fair use:
-Purpose and character of your use (educational? commercial (i.e. to make money)? comment or criticism? etc.);
-Nature of the copyrighted work (more creative = more protection: fiction book gets more protection than fact-based article b/c facts aren’t copyrightable);
-Amount and substantiality of the portion used (how much of the work was used? does it go to “heart of the matter?”); and
-Effect on potential market (not just effect on current market. might someone use the infringing work instead of something from the copyright owner?
This article is for informational and educational purposes only. This should not be taken as a substitute for legal advice. This does not create an attorney-client relationship with anyone who reads it.
Source: Quora