The OutSystems Platform provides single sign-on capabilities by default: after authenticating in one of the applications, end-users are able to access all other applications without having to provide the credentials for each application they access.
By default, all applications created have single sign-on capabilities, since their User Provider module is set to the Users system module. However, if you are using a different user provider:
In a Single Sign-On scenario, check out your unified modules in Service Center: edit an module and select the 'Single Sign-On' tab to see the User Provider module and User Subscriber modules.
The User Provider module contains an entity that stores end-users information. This entity is set with the 'Public' property to 'Yes' so that it can be reused by User Subscriber modules. Learn more about Reusing Entities.
To authenticate an end-user, simply check if the provided credentials match any record existing in the entity of the User Provider module.
The session is created the first time the end-user accesses the server to request a page of any unified module. However, since the session is shared by the unified modules, the first On Session Start action to be invoked is the one of the User Provider module. Only then, if there is an On Session Start action in the requested module, it is invoked.
From then on, the On Session Start actions of the User Subscriber modules are invoked the first time each module is accessed via a screen, web block, or public action.
In a Single Sign-On situation, there is only one session shared by the unified modules which consists of all the session variables defined in these modules. If you need to reference or change a session variable from another module, you must use public actions, since there is no other way to add and remove session references between modules.
Note that sharing session variables through public actions only works for unified modules of the same set. Otherwise, as you will have different sessions, you will refer to different variables from each module. See Use eSpace References.
About End-User Authentication | eSpace Properties