What is SCIM, and what problem does it solve?

SCIM, the System for Cross-domain Identity Management, is an open standard that automates user provisioning: it defines a common schema for users and groups and a REST API for creating, updating and deactivating them in target systems.

Before SCIM, every cloud application had its own proprietary API for user management, so an organisation that wanted accounts created automatically in twenty SaaS tools had to build and maintain twenty connectors. SCIM standardises both halves of the problem:

• A schema: a common JSON representation of a user (identifier, name, e-mails, active flag, group memberships) and of groups.
• A protocol: HTTP operations to create, read, update, patch and delete these resources.

An identity system can therefore push the same "Alice joined, Alice changed department, Alice left" events to any SCIM-capable application. It is the provisioning counterpart of what SAML and OpenID Connect are for federation.

Go deeper:

• RFC 7644 SCIM Protocol — the REST operations themselves; RFC 7643 defines the schema.
• SCIM (Wikipedia) — overview of the standard, its history and adoption.
• SCIM community site (simplecloud.info) — the specification hub with an overview and links to the SCIM 2.0 documents.