What is the primary search tool used by patent examiners for classified searching?

The primary search tool used by patent examiners for classified searching is the Cooperative Patent Classification (CPC) system. According to MPEP 904.02(a):

“The primary classification search tool is the Cooperative Patent Classification (CPC) system.”

The CPC system is a collaborative effort between the USPTO and the European Patent Office (EPO) to provide a harmonized patent classification system.

To learn more:

• CPC
• Cooperative Patent Classification
• patent search
• classified search