gtag('set', {'user_id': 'USER_ID'}); // Set the user ID using signed-in user_id. ga('set', 'userId', 'USER_ID'); // Set the user ID using signed-in user_id. gtag('set', {'user_id': 'USER_ID'}); // Set the user ID using signed-in user_id. ga('set', 'userId', 'USER_ID'); // Set the user ID using signed-in user_id.