Conduct a Patent Number Search

The U.S. Patent and Trademark Office (USPTO) website is a primary resource for searching U.S. patents, and in particular, to conduct a patent number search. There are a number of other resources that are also available to conduct patent number searches. Some resources allow a user to conduct only a U.S. patent search. However, other resources allow a user to conduct a foreign patent number search.

For example, the following is a list of resources that provide a mechanism to conduct a patent number search:

  • World Intellectual Property

  • Google Patents

  • European Patent Office

  • U.S. Patent Search


  • FreePatentsOnline

A patent number search need not always include any World Intellectual Property Organization (WIPO) Standard ST.16 codes, but most patent number search databases recognize the codes. Generally, the WIPO Standard ST.16 codes (kind codes) include a letter, and in many cases followed by a number, used to distinguish the kind of patent document (e.g., patent application publication versus a patent) and the level of publication (e.g., first publication, second publication, or corrected publication), respectively.

Typically, the patent number search should identify USPTO documents using the following three elements:

1) the two-character country code (US);

2) the patent or publication number; and

3) the WIPO ST.16 kind code.

For example, the term "US 7,333,321 B1" could be used in a patent number search for U.S. Patent 7,333,321. The WIPO ST.16 kind code indicates that there has been no previously published patent application. As another example, the term "US 2008/333567 A1" could be used in a patent number search for U.S. Patent Application Publication No. 2008/333567, published in 2008.

If for some reason the patent number search is unsuccessful, there is a chance that the USPTO has chosen not to make the patent reference publicly available. The USPTO offers a list of patent numbers that are not available on the USPTO website: When an owner (or the USPTO) withdraws a patent, a search will not be successful.  To find a list of withdrawn issued patents:

Please note that before investing in any patent application, it is advisable to conduct a prior art search. Such search should include an investigation of known references through a patent number search, for any possible blocking patents. A prior art search could help the inventor assess the scope of protection available, where to file patent applications, and take measures to prevent possible infringement of existing patents. Results from a prior art search and a patent number search could also aid in drafting the patent application and, ultimately, in deciding the scope of the claims.

About the Firm:

Klemchuk LLP is an Intellectual Property (IP), Technology, Internet, and Business law firm.  The firm offers comprehensive legal services including litigation and enforcement of all forms of IP as well as registration and licensing of patents, trademarks, trade dress, and copyrights.  The firm also provides a wide range of technology, Internet, e-commerce, and business services including business planning, formation, and financing, mergers and acquisitions, business litigation, data privacy, and domain name dispute resolution.  Additional information about the IP law firm and its IP law attorneys may be found at

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