Auth0 Multi-Application Authentication Architecture

Introduction Building a modern SaaS platform often means supporting multiple frontend applications - a customer-facing web app, an admin dashboard, a mobile app for coaches, and perhaps more. Each application has different user roles, different access requirements, and different security considerations. Yet they all need to authenticate against the same user base and access shared backend services. This is the multi-application authentication challenge : how do you maintain a single source of truth for user identity while supporting diverse client applications with varying security requirements? The naive approach of creating separate Auth0 tenants for each app quickly becomes a nightmare of duplicated users, inconsistent permissions, and maintenance overhead. In this article, I'll walk through a battle-tested architecture for handling multi-application authentication with Auth0. We'll cover tenant configuration, role-based access control (RBAC), token validation middleware, and the co