As much as European integration is characterised by differentiation, so is national implementation as well as enforcement. Differentiated implementation challenges the EU’s ability to establish a level playing field and achieve collective objectives. European Administrative Networks (EANs) constitute important instruments to address this challenge. Despite the surge of literature recognising the importance of these networks, we still know little when it comes to their numbers, characteristics, functions and functioning among other aspects. This paper provides a systematic mapping of EANs across five policy areas: internal market, health, social protection, asylum and immigration, and environment. The paper furthermore examines the functions and functioning for a subset of networks. We find that EANs have increasingly become part of the European Administrative Space but vary when it comes to formalisation and independence as well as functions and functioning. While EANs stand out as important instruments to reduce differentiated implementation, they do not do so equally across the board.