Configuration Steps

1. Create both applications in the same tenant - Users are scoped at the tenant level, so applications in the same tenant can share authentication state through FusionAuth's SSO session.

2. Enable self-service registration on the second application - This ensures a seamless login experience. When a user navigates to the second application while already authenticated to the first, they will be automatically registered and logged in.

How It Works

• User logs into the first application at your registration URL to create their account. Make sure the rememberDevice parameter is true or checked. You can modify your theme to hardcode that value.
• While that session is valid, they navigate to the second application's login URL
• They are automatically registered and authenticated to the second application without manual intervention

The key to this working is that FusionAuth creates an SSO session at the tenant level when a user logs in and rememberDevice is checked. When the authenticated user tries to access the second application, FusionAuth recognizes the existing SSO session and automatically creates a registration for that user in the second application (when self-service registration is enabled).

Password Reset Behavior

Because users are scoped at the tenant level, a password reset applies to all applications under that tenant. Users can utilize the password reset page for the first application and will be able to log in at the second application with the new password.

Sharing Templates

Both applications can share the same theme and templates. Themes are assigned at the tenant level (though you can also assign application-specific themes if needed starting with FusionAuth 1.27+). This means you can configure one set of templates - including password reset, login, and user management pages - that will be used by both applications.

Pre-creating User Accounts

If you create user accounts ahead of time, you can automatically include the registration for the second application when creating the users. This would mean adding that application to their registrations when you create the account initially using the Create a User and Registration API.

Related Documentation

• Implementing Single Sign-On - Complete guide to configuring SSO between applications
• Self-Service Registration - How automatic registration works when SSO is enabled
• Create a User Registration API - Programmatically register existing users to additional applications
• Application Themes - Configure application-specific themes if needed
• Themes Documentation - Customize and share login pages and templates across applications