The APOC library is a set of standard user-defined procedures to extend Cypher in Neo4j. User-defined procedures are custom implementations of certain functionality that cannot be easily expressed in Cypher. They are implemented in Java, so they are deployable to a Neo4j instance and callable directly from Cypher.

The APOC library consists of over 450 procedures to help with many different tasks in areas like data integration, data conversion, and much more.