AzureAD App Registrations explained

Azure AD App registration

Recently I had some talks with developers which made me to realize that I didn’t fully understand how App Registrations are working. I was aware that we are registering an app and allowing the app certain permissions but in detail I didn’t understand it.

Why Azure AD App registration?

Basically for every app where you want to use the Microsoft Identity Platform, you need to register your app. So you want to login into a certain webapp with your Microsoft Account? This app needs to be registered in Azure AD. After you logged in into your application, this app maybe also need some data of your Microsoft Account and you maybe need to grant perrmissions.

There are two main concepts behind that:

1. Authentication

  • The process of proving who you say you are.
  • Verification of the identity of a person or device.
  • short: AuthN
  • used protocol:

2. Authorization

  • Granting an authenticated party permission to do something.
  • short: AuthZ
  • used protocol: OAuth 2.0

Basics of OpenID Connect (OIDC) - OAUTH2

To understand how App registrations are working I started with this video of John: John Savill - Azure AD App Registrations, Enterprise Apps and Service Principals
He first started to explain th basics of OpenID Connect and OAUTH2.

From this video I created this picture to understand how OpenID Connect - Oauth2 is working:


Watch the Video of John to get a better idea how this is working.

Register an App

So now we switch to Azure AD. A developer has for example his HikingApp where he would like to use Azure AD as Identity Provider. The HikingApp will be running as SaaS in his own tenant. So the developer now needs to register his app in his Azure Tenant:


  1. Developer wants to register his app in his Tenant
  2. He creates an App Registration which creates a globally unique Application Object
  3. During the creation of the App Registration it’s necessary to select:
    1. supported Account types
    2. Redirect URI
      1. (place where authorization server redirects the user)
  4. The App Registration process in the portal automatically creates a Service Principal (Listed in Enterprise Apps)

What happens when a user is opening this HikingApp for the first time?


  1. User 1 navigates to the Webpage and signs in with his Microsoft Account
    1. At the first login attempt the users needs to consent permissions
  2. This will create a Service Principal in the user tenant
    1. which references to the globally unique Application Object

Authentication Concepts - MindMap

This MindMap tries to give an Overview over some core Authentication Concepts related to Azure AD: