Devise

Devise is a flexible authentication solution for Rails based on Warden. You will install Devise as a gem, and then run the generator to create the necessary configuration files. Devise comes with a set of views for authentication, but you will want to generate views of your own to customize the look and feel of your application.

Using Devise, you can create users, log them in and out, and restrict access to certain pages based on the current_user. Devise also provides a number of useful helper methods for controllers and views.

Devise does not provide authorization functionality, so you will need to use another Ruby gem for that.