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Patents: How to Search For a U.S. Patent

Guide to searching among United States and foreign patents (prior art) to determine whether an idea can be patented.

Seven Step Strategy

Where and How to Search for a Patent


A patent search is performed by an inventor to determine if "prior art", that is, his or her invention already exists or has been patented in the United States or elsewhere in the world.  A patent search is also necessary to compile any similar domestic or foreign patents or industry literature for the Information Disclosure Statement which is required in a U.S. patent application.  Conducting a thorough patent search better prepares you for meeting with potential patent attorneys to discuss your patent.  The official database of record of United States patents resides in the USPTO website.  Here, United States patents can be researched and retrieved from the first year patents were granted in 1790 to the most recent weekly update.  Please refer to the following guide.

One can search for patents using keywords but that is not recommended because-

  • patents granted between 1790 and 1975 are not keyword searchable, they are only retrievable by the patent number, the Cooperative Patent Classification (CPC) number or the United States Patent Classification (USPC) number
  • there are often many synonyms for a similar area of technology

The best search strategy is to think of all terms which can be used to describe your invention.  Look up these terms in the keyword search field located in the Classification Text Search box on the right side of the page to find the relevant Cooperative Patent Classification (CPC) number.  Each area of technology is identified by a CPC number.  The CPC Classification Scheme is largely based on the International Patent Classification (IPC) system and was developed jointly by the USPTO and the European Patent Office (EPO) and it can be browsed starting with its main headings.  The USPTO started classifying all granted patents and patent applications using only the CPC since January 1, 2015.  Patents between 1790 and 2015 were classified by the United States Patent Classification (USPC) schedule.  The corresponding CPC numbers have been added retrospectively to these older patents.

**As of February 1, 2022 the USPTO began migrating the patent search interface to Public Patent Search which will eventually replace PatFT and AppFT available on as well as PubEAST and PubWEST which are only accessible to searchers in a Patent and Trademark Resource Center.

All newly issued patents are published weekly in the Official Gazette for Patents which is retrospectively accessible online beginning with the issue dated July 2, 2002.  The preceding years beginning with volume 1 (1872) are available online via the Hathi Trust.

You should also consider broadening your search to other databases freely available online as well as the internet and literature published in that area of technology.