You don’t need to implement your own “remember me” with Local Storage. OutSystems mobile (and Reactive) already supports persistent login natively, and that’s both the recommended and the most efficient approach.

1. Use the built‑in persistent login

In your login logic, call the system action User_Login with:

• Username / Password: user credentials
• RememberLogin = True

When RememberLogin is True, OutSystems issues persistent authentication cookies/tokens so that, after the first login, the user doesn’t need to re‑enter credentials unless:

• The user logs out (via User_Logout), or
• The persistent login expires (idle time or max lifetime).

This is the official “remember me” mechanism for Mobile and Reactive apps. Persistent Login

2. Configure how long “login once” lasts

Environment-wide settings are configured in Service Center:

• Cache Time (minutes) – validity of cached auth info before issuing new tokens.
• Persistent authentication:
  • Max Idle Time (days) – maximum days without activity before forcing re-login.
  • Cookie Expiration (days) – absolute maximum duration of the persistent login.

For mobile apps, these settings control how long “log in once” actually means in practice. Set security for an environment

3. Startup flow (no noticeable delay)

On your initial “splash” or “launch” screen:

1. Call CheckSession() (or simply rely on GetUserId() / Session.UserId) from a server/logic flow to see if the user is authenticated.
2. If authenticated → redirect immediately to Home.
3. If not → redirect to Login.

Because the platform manages cookies/tokens under the hood and they’re checked on the first server call, you don’t need extra Local Storage checks. The server-side authentication lookup is already optimized and typically very fast.

4. Avoid storing credentials in Local Storage

Do not store the username/password locally (even encrypted):

• If the device is compromised, stored credentials can be abused.
• OutSystems docs recommend using tokens / persistent auth rather than keeping passwords. [Security login mobile app] Is it safe to save the password with the username ?

If you need to remember some user context locally (e.g., last logged-in username, preferences), use Client Variables / Local Storage for non-sensitive data only.

5. Optional: extra security

Depending on your use case:

• Add a simple PIN or biometric check in the app before entering Home, to protect access if someone else uses the device. [Security login mobile app] Is it safe to save the password with the username ?

Summary:
Use User_Login with RememberLogin=True + configure persistent authentication in Service Center, and on app startup just check if the session is authenticated and redirect accordingly. This gives you secure, fast, and native persistent login without managing Local Storage yourself.