Certain information and activity existing before the filing date of a patent application and satisfying certain other conditions that qualify it for use in determining the patentability or validity of the claimed invention.

The federal Patent Act, as amended by the Leahy-Smith America Invents Act (AIA), identifies the specific types of information and activities that qualify as prior art (35 U.S.C. § 102). The AIA amendments transitioned the US from a first-to-invent to a first-inventor-to-file system and generally apply to patent applications and patents with an effective filing date on or after March 16, 2013. What qualifies as prior art may differ depending on whether pre-AIA or AIA law applies.

For detailed information on determining the prior art status of a reference or activity, see Practice Notes, Prior Art: Determining the Status of a Reference and Prior Art: Public Use, On Sale, Knowledge, and Availability.