Glossary
Modern Authentication
OAuth 2.0-based authentication in Microsoft 365, supporting MFA, Conditional Access, and tokenized sign-in.
Modern authentication is Microsoft's term for OAuth 2.0-based authentication in Microsoft 365, replacing the older basic authentication model. With modern auth, clients sign users in via Microsoft Entra ID using interactive OAuth flows, receive access tokens and refresh tokens, and present those tokens to resource services. Modern auth supports MFA, Conditional Access, Continuous Access Evaluation, token protection, risk signals, and the full modern security stack — none of which work with basic authentication. As of 2026, basic auth is effectively removed from Exchange Online; modern auth is the default everywhere. Required for all current Microsoft 365 clients (new Outlook, Teams, Office apps).