The present document formally describes the Context Information Management API (NGSI-LD) Specification. The Context Information Management API allows users to provide, consume and subscribe to context information in multiple scenarios and involving multiple stakeholders. Context information is modelled as attributes (properties and relationships) of context entities, also referred to as "digital twins", representing real-world assets. It enables close to real-time access to information coming from many different sources (not only IoT data sources).