Fair use is a rule in copyright that allows certain limited use of a work without the permission of or paying a royalty to the holder of a copyright. It covers situations such as quoting a portion of a larger work, copying a television broadcast to the hard drive of a digital video recorder, distributing pages of a book to a classroom, or lending out books from a library.

The term "fair use" is exclusive to American law, but other common law jurisdictions have a similar concept known as "fair dealing" and civil code jurisdictions also recognize similar restrictions on the rights of a copyright holder. To all intents and purposes, although there are some differences, the rules in most juridictions are similar enough to be fairly compared. The four issues a court will consider are:

  • What is the nature of the use? (Non-commercial uses are looked on more favorably than commercial ones)
  • What is the nature of the copyrighted work? (Works of non-fiction will generally contain factual information that cannot be fully protected by copyright)
  • What proportion of the original work has been copied? (An excerpt of a poem will most likely not be covered, while a similar sized portion of a novel might be).
  • What is the effect of the copying on a work's value? (An excerpt in a book review is most likely protected, even if it is negative, because of the value of book reviews to the sale of books as a whole).

The party wishing to rely on fair use usually has the burden of showing the use was fair.

Some examples:

  • Under U.S. law, posting thumbnails of pictures that link to the original picture is considered to be fair use.
  • Under Canadian law, libraries providing copies of legal texts to researchers is fair dealing.