Microsoft Graph

Microsoft Graph is Microsoft's unified API gateway for accessing data across Microsoft 365, Windows, and Enterprise Mobility + Security.

With a single endpoint (graph.microsoft.com), it provides comprehensive access to services like Outlook, Teams, OneDrive, SharePoint, and Azure AD. The API uses OAuth 2.0 authentication with both delegated and application permissions. Documentation is excellent with interactive Graph Explorer for testing. SDKs are available for all major languages. The API supports both v1.0 (GA) and beta endpoints. Rate limiting and throttling policies are in place.

It's ideal for building productivity apps, automation tools, and enterprise integrations across the Microsoft ecosystem.