Four factors are used as a guideline when considering whether the use of a work is "fair use."

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The four factors are:

• the purpose and character of the use, which includes whether the use is for nonprofit educational purposes or commercial in nature, as well as whether the work is transformed in some manner or simply reproduced (see Transformativeness below);
• the nature of the copyrighted work, such as whether it is technical vs. artistic, factual vs. imaginative, and published vs. unpublished (Fair Use favors technical, factual, published works);
• the amount and substantiality of the portion used in relation to the whole, however, use of even a small portion of the work may violate Fair Use if that portion is the "heart" of the work;
• the effect of the use on the market which includes competition with the original work that may deprive the copyright owner of income, or that undermines a new or potential market for the copyrighted work.

Simply providing an acknowledgement of a work does not make it permissible to use that work or a portion of it. One example is using an image from a book or magazine and including the name of the photographer or artist. Acknowledgment of the source material does not protect against an infringement claim. Risk of infringement exists even when you make use of personal photographs of textual or visual works produced by others. If you have any doubt about the right to use, the best approach is to seek the permission of the copyright owner.

Transformativeness is defined by whether 1) value is added to the original by creating new information, new aesthetics, new insights and understandings, and 2) whether the material taken from the original work has been transformed by adding new expression or meaning. Parody is a common example of transformative use.

The University of Minnesota has a helpful discussion of Fair Use that includes example scenarios.