In 2013, the U.S. Patent and Trademark Office (PTO) began transitioning from the US Patent Classification (USPC) system to the Cooperative Patent Classification (CPC) system. Prior to that time, U.S. patents included only USPC codes. In 2013 and 2014, U.S. patents were assigned both USPC and CPC codes. In 2015, the PTO began issuing patents with only CPC codes and assigned CPC codes for older patents, except for design and plant patents which continue to issue with USPC codes.

Both systems allow patents to be tagged with more than one classification when the patent overlaps several areas. The USPC system is not inherently hierarchical, however the National Bureau of Economic Research organized the approximately 600 USPC codes into six categories and 39 subcategories. The CPC system is inherently hierarchical with nine top-level divisions, 126 subcategories, and about 650 4-digit CPC codes (all subject to revision). Both the USPC and the CPC divide these codes into multiple levels of subcodes.

Docket Navigator tags litigated patents with either both USPC and CPC codes when the data is available from the PTO. The complete list of codes and their titles is available on the Abstract tab of the patent detail page under the headings: Main U.S. Patent Class, Other U.S. Patent Classes, U.S. Patent Class Search Field, and Cooperative Patent Classes. The complete list of subcodes are available under the headings: U.S. Patent Class subcodes and Cooperative Patent Classes subcodes.

A search by patent class in Docket Navigator returns patents, or other items associated with those patents, which are tagged with any of the specified USPC or CPC class codes. Selecting the criteria shows a hierarchical arrangement with both the USPC and CPC classes at the highest level. A search may include categories from either or both systems.