Under certain circumstances it is permissible to exercise one of the exclusive rights of the copyright owner without first obtaining permission. You may use or copy copyrighted materials without the copyright owner’s permission where such use or copying constitutes “fair use” under the Copyright Act. Determining whether a proposed use constitutes “fair use” involves applying a four-factor test established by copyright law. The four factors are:

• The character of the use (e.g., educational vs. commercial);
• The nature of the work to be used (e.g., factual vs. creative);
• The amount of the work to be used (a lot or a little); and
• The effect such use would have on the market for the original or for permissions, if the use were widespread.

It is not always easy to apply this test and everyone does not always agree on the outcome in any given case. The University of Texas has a webpage that contains an explanation of fair use written by Georgia Harper, a leading expert in copyright law. A handy checklist can be found here.