When registering a web application in Azure AD to enable authentication, the Redirect URI (also known as a reply URL) is a critical security configuration. After a user successfully authenticates with the Microsoft identity platform, Azure AD redirects the user's browser back to this specific URI. The redirection includes the security token (an ID token or access token) required by the application to complete the sign-in process and verify the user's identity. Without a correctly configured Redirect URI, the authentication flow cannot be completed, and the application will not receive the necessary token.

A. The executable name is not a standard configuration property for a web app registration in Azure AD; it is more relevant for identifying native desktop applications.

B. The bundle ID is a unique identifier required when registering native applications for Apple's iOS or macOS platforms, not for a .NET web app.

C. The package name is a unique identifier required when registering native applications for the Android platform, not for a .NET web app.

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1. Microsoft identity platform documentation

"Quickstart: Register an application with the Microsoft identity platform."

Reference: Under the section "Register an application

" step 5

"Add a redirect URI

" it states: "Select the platform for your application - Web... Enter the redirect URI for your application." This explicitly shows that for a web app

the redirect URI is a required configuration.

Source: https://docs.microsoft.com/en-us/azure/active-directory/develop/quickstart-register-app#register-an-application

2. Microsoft identity platform documentation

"Redirect URI (reply URL) restrictions and limitations."

Reference: The document's overview section states

"A redirect URI

or reply URL

is the location where the Microsoft identity platform redirects a user's client and sends security tokens after authentication. For example

in a web application

the redirect URI is the location where the user is sent after they sign in."

Source: https://docs.microsoft.com/en-us/azure/active-directory/develop/reply-url

3. Microsoft Learn

SC-300 Courseware

"Register an application."

Reference: In the learning module for implementing application access

the section on app registration details the required settings. It specifies: "When you register a web app

you must add a redirect URI. The redirect URI is the URI where users are sent after they've been authenticated." It also shows that Package Name and Bundle ID are for mobile platforms.

Source: https://learn.microsoft.com/en-us/training/modules/implement-manage-app-permissions/2-register-app