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Authentication scenarios and recommendations

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If you have a web app or an API running in Azure App Service, you can restrict access to it based on the identity of the users or applications that request it. App Service offers several authentication solutions to help you achieve this goal. In this article, you will learn about the different authentication options, their benefits and drawbacks, and which authentication solution to use for specific scenarios.

Authentication solutions

  • Azure App Service built-in authentication - Allows you to sign users in and access data by writing minimal or no code in your web app, RESTful API, or mobile back end. It’s built directly into the platform and doesn’t require any particular language, library, security expertise, or even any code to use.
  • Microsoft Authentication Library (MSAL) - Enables developers to acquire security tokens from the Microsoft identity platform to authenticate users and access secured web APIs. Available for multiple supported platforms and frameworks, these are general purpose libraries that can be used in various hosted environments. Developers can also integrate with multiple sign-in providers, like Microsoft Entra, Facebook, Google, Twitter.
  • Microsoft.Identity.Web - A higher-level library wrapping MSAL.NET, it provides a set of ASP.NET Core abstractions that simplify adding authentication support to web apps and web APIs integrating with the Microsoft identity platform. It provides a single-surface API convenience layer that ties together ASP.NET Core, its authentication middleware, and MSAL.NET. This library can be used in apps in various hosted environments. You can integrate with multiple sign-in providers, like Microsoft Entra, Facebook, Google, Twitter.

Scenario recommendations

The following table lists each authentication solution and some important factors for when you would use it.

Authentication method When to use
Built-in App Service authentication * You want less code to own and manage.
* Your app's language and SDKs don't provide user sign-in or authorization.
* You don't have the ability to modify your app code (for example, when migrating legacy apps).
* You need to handle authentication through configuration and not code.
* You need to sign in external or social users.
Microsoft Authentication Library (MSAL) * You need a code solution in one of several different languages
* You need to add custom authorization logic.
* You need to support incremental consent.
* You need information about the signed-in user in your code.
* You need to sign in external or social users.
* Your app needs to handle the access token expiring without making the user sign in again.
Microsoft.Identity.Web * You have an ASP.NET Core app.
* You need single sign-on support in your IDE during local development.
* You need to add custom authorization logic.
* You need to support incremental consent.
* You need conditional access in your web app.
* You need information about the signed-in user in your code.
* You need to sign in external or social users.
* Your app needs to handle the access token expiring without making the user sign in again.

The following table lists authentication scenarios and the authentication solution(s) you would use.

Scenario App Service built-in auth Microsoft Authentication Library Microsoft.Identity.Web
Need a fast and simple way to limit access to users in your organization? ✅ ❌ ❌
Unable to modify the application code (app migration scenario)? ✅ ❌ ❌
Your app's language and libraries support user sign-in/authorization? ❌ ✅ ✅
Even if you can use a code solution, would you rather not use libraries? Don't want the maintenance burden? ✅ ❌ ❌
Does your web app need to provide incremental consent? ❌ ✅ ✅
Do you need conditional access in your web app? ❌ ❌ ✅
Your app need to handle the access token expiring without making the user sign in again (use a refresh token)? ✅ ✅ ✅
Need custom authorization logic or info about the signed-in user? ❌ ✅ ✅
Need to sign in users from external or social identity providers? ✅ ✅ ✅
You have an ASP.NET Core app? ✅ ❌ ✅
You have a single page app or static web app? ✅ ✅ ✅
Want Visual Studio integration? ❌ ❌ ✅
Need single sign-on support in your IDE during local development? ❌ ❌ ✅

Next steps

To get started with built-in App Service authentication, read:

To get started with Microsoft Authentication Library (MSAL), read:

To get started with Microsoft.Identity.Web, read:

Learn more about App Service built-in authentication and authorization