React Native - Firebase auth persistence not working

Make sure you do not restrict the 'Token Service API' in the console, with the API key you are using. I did not add the service to my key, and it logged me out every 3-4 hours, even with the right code suggested above.

You don't need to set persistence. Firebase handles it for you by default. You just need to call this function to check whether user is logged or not:

firebase.auth().onAuthStateChanged((user) => {
      if (user) {
        console.log('user is logged');
      }
});

This will not be triggered only if user has sign out or cleaned app data.

You can find more details in the official docs: https://firebase.google.com/docs/auth/web/manage-users

Hope it helps.