A review of existing patents. Patent searches are conducted to determine whether an applicant can claim rights to an invention, or whether a patent has already been issued to someone else on the same or a similar invention. Patent infringement searches are made to ascertain whether a product or process can be produced without having to get permission or pay a royalty. Patent searches are also used as a form of research to gain information on existing technology.

A study of the patent literature to determine the state of the art in a particular field; a study of the patent literature in a particular field to determine whether the prior art in the field renders a particular invention anticipated or obvious, and, hence, not able to receive a patent.

A search for documents that will determine whether a particular invention was novel and nonobvious when it was invented, and hence whether it may qualify for a patent. A patent search usually begins with a database of previously issued patents, and also covers other types of documents, such as journal articles and scientific papers, that describe unpatented inventions.