This document summarizes the scope and general principles of coordination under EU social security regulations. It outlines the personal scope, which broadly covers EU citizens and their family members who are subject to social security legislation in one or more member states. It also describes the material scope, which primarily includes social security benefits but excludes social assistance. The key coordination principles are then summarized as equal treatment, assimilation of facts, aggregation of periods, export of benefits, and administrative cooperation between member state institutions.