SCIM (System for Cross-domain Identity Management) is an open, HTTP-based protocol designed to simplify the management of user identities across multiple systems by providing a common set of rules for exchanging user information. It automates the process of adding, updating, and removing users, ensuring consistency and security while reducing the risk of errors. SCIM is particularly useful in large organizations to manage user data across various services like email, payroll, and project management when onboarding or updating employee information. It works alongside identity management standards such as SAML and SSO, and typically involves a "client" like an identity provider to authenticate users and "service providers" like software services to maintain user data. SCIM's REST API and core schema enable seamless data synchronization, making it easier to keep multiple systems updated with accurate user information. The protocol is widely adopted by major identity providers and supports interoperability through standard data types and attributes, which can be customized for specific needs. Additionally, services like Merge offer a Unified API to integrate SCIM-compliant services, further streamlining the integration of identity management systems across various platforms.