Auth0 saves developers from building login systems themselves, which is a task where mistakes are costly. You add its SDK to an app, and it handles sign-up, login, password reset, social logins like Google or Apple, and passwordless options such as one-time codes and passkeys. It can connect to company identity providers for single sign-on, apply multi-factor and adaptive authentication, and manage roles and permissions. A hosted login page can be customized to match your brand.
The platform has grown to cover the new needs of AI applications. Auth for AI Agents lets agents act on a user’s behalf with scoped permissions, securely storing and exchanging tokens for connected services, and it supports authentication for tools that use the Model Context Protocol. For regular apps, rules and actions let you run custom code at points in the login flow, and logs and anomaly detection help spot attacks.
Auth0 has a free plan that is generous for small apps, with paid plans priced by monthly active users and features, and enterprise options. Costs rise noticeably as users grow, which is the main reason some teams switch. Okta’s ownership means it is stable and well supported. Competitors include Clerk, Firebase Authentication, AWS Cognito, Supabase Auth, and the open-source Keycloak, which can be self-hosted.