MFA for Entra External ID, explained for app builders

Microsoft Entra External ID allows app developers to implement multi-factor authentication for external users through a dedicated tenant that separates customer security from internal employee policies. By leveraging user flows and Conditional Access policies, developers can choose between various verification methods—such as email OTP or phishing-resistant FIDO2 passkeys—and enforce them based on specific risk levels. The platform also supports "step-up" authentication, enabling stronger identity challenges only when users attempt sensitive actions within an application.