If you want a solution for session management - i.e. user logs into your site and then you want to keep that user logged in for a long time, securely, you should use SuperTokens (I am biased here, of course). If you want a full user management solution and don't mind saving all your user's info in a third party app's servers, you can use Auth0 or Okta or Cognito. But these services do not provide a good session management solution - so you would have to use something like SuperTokens or if you are using node, then express-sessions etc..