What is Azure Active Directory (Azure AD / Entra ID)?

Azure Active Directory (now rebranded as Microsoft Entra ID) is Microsoft's cloud-based identity and access management service. It provides authentication and authorization for Azure resources, Microsoft 365, and thousands of third-party SaaS apps. Key features: Single Sign-On (SSO) across apps. Multi-Factor Authentication (MFA). Conditional Access policies. B2B collaboration for external users. B2C for customer-facing identity. Azure AD differs from traditional Windows Active Directory — it is designed for web/cloud protocols (OAuth 2.0, OpenID Connect, SAML) rather than on-premises Kerberos/LDAP. Most Azure services and Microsoft applications use Azure AD for authentication.