title: Thinktecture Identity server vs Authorization server
body: <p>I am researching on this topic last weeks and unfortunately I can't figure out. I understand the difference between authentication and authorization.</p>
  
  <p>I will appreciate any guidance on the topic.</p>
  
  <p>What I need as general is to implement single sign on for several web sites which are driven with apis which also should handle authentication. The users should be able to register/login with username/pass or respectively through any third party service like facebook, google+, twitter etc.</p>
  
  <p>In the scenario above what is the better approach? Should I use only identity server, or only authorization server or both?</p>
  
  <p>Thank you in advance.</p>