Devise handles authentication across the entire stack. It you’re familiar with Authlogic which was covered back in episode 160 [watch , read ] you’ll know that it covers just the model layer. By comparison, devise is a Rails Engine and covers controllers and views as well. Devise is modular and currently consists of eleven modules, each of which provides a different aspect of authentication. For example one module, Rememberable, remembers the user’s authentication in a saved cookie while another, Recoverable, looks after resetting the user’s password and sending reset instructions. This approach makes it easy to choose which parts of the authentication you want to use in your applications.