A validity search is a search that is determined by the selected claims of an issued patent. Validity searches might be required for a number of reasons. Sometimes, the validity of a patent is brought up during litigation. Oftentimes, a validity search is requested even when no lawsuit has been filed, to identify potential attackers and/or references that challenge the presumption of validity of a subject patent.

A validity search also helps with the valuation of a patent. If the searcher discovers closely related prior art that may cast doubt on the validity of the subject patent, the patent may be considered “weak”. On the other hand, if the search does not discover these other documents, the subject patent may be considered “strong”. This kind of investigation plays in important role when licensing agreements or other royalties are being negotiated between the subject patent holder and a 3rd party interested in practicing its claimed subject matter.