Register a single-page application in Azure Active Directory B2C

Before your applications can interact with Azure Active Directory B2C (Azure AD B2C), they must be registered in a tenant that you manage. This guide shows you how to register a single-page application ("SPA") using the Azure portal.

Overview of authentication options

Many modern web applications are built as client-side single-page applications ("SPAs"). Developers write them by using JavaScript or an SPA framework such as Angular, Vue, and React. These applications run on a web browser and have different authentication characteristics than traditional server-side web applications.

Azure AD B2C provides two options to enable single-page applications to sign in users and get tokens to access back-end services or web APIs:

Authorization code flow (with PKCE)

OAuth 2.0 Authorization code flow (with PKCE) allows the application to exchange an authorization code for ID tokens to represent the authenticated user and Access tokens needed to call protected APIs. In addition, it returns Refresh tokens that provide long-term access to resources on behalf of users without requiring interaction with those users.

This is the recommended approach. Having limited-lifetime refresh tokens helps your application adapt to modern browser cookie privacy limitations, like Safari ITP.

To take advantage of this flow, your application can use an authentication library that supports it, like MSAL.js.

Implicit grant flow

Some libraries, like MSAL.js 1.x, only support the implicit grant flow or your applications is implemented to use implicit flow. In these cases, Azure AD B2C supports the OAuth 2.0 implicit flow. The implicit grant flow allows the application to get ID and Access tokens. Unlike the authorization code flow, implicit grant flow doesn't return a Refresh token.

This authentication flow doesn't include application scenarios that use cross-platform JavaScript frameworks such as Electron and React-Native. Those scenarios require further capabilities for interaction with the native platforms.

Prerequisites

• If you don't have an Azure subscription, create a free account before you begin.

• If you don't have an Azure AD B2C Tenant, create one now. You can use an existing Azure AD B2C tenant.

Register the SPA application

1. Sign in to the Azure portal.

2. If you have access to multiple tenants, select the Settings icon in the top menu to switch to your Azure AD B2C tenant from the Directories + subscriptions menu.

3. In the Azure portal, search for and select Azure AD B2C.

4. Select App registrations, and then select New registration.

5. Enter a Name for the application. For example, spaapp1.

6. Under Supported account types, select Accounts in any identity provider or organizational directory (for authenticating users with user flows)

7. Under Redirect URI, select Single-page application (SPA), and then enter https://jwt.ms in the URL text box.

   The redirect URI is the endpoint to where authorization server (Azure AD B2C, in this case) sends the user after it completes its interaction with the user. Also, the redirect URI endpoint receives the access token or authorization code upon successful authorization. In a production application, it's typically a publicly accessible endpoint where your app is running, like https://contoso.com/auth-response. For testing purposes like this guide, you can set it to https://jwt.ms, a Microsoft-owned web application that displays the decoded contents of a token (the contents of the token never leave your browser). During app development, you might add the endpoint where your application listens locally, like http://localhost:5000. You can add and modify redirect URIs in your registered applications at any time.

   The following restrictions apply to redirect URIs:

   • The reply URL must begin with the scheme https, unless using localhost.
   • The reply URL is case-sensitive. Its case must match the case of the URL path of your running application. For example, if your application includes as part of its path .../abc/response-oidc, don't specify .../ABC/response-oidc in the reply URL. Because the web browser treats paths as case-sensitive, cookies associated with .../abc/response-oidc may be excluded if redirected to the case-mismatched .../ABC/response-oidc URL.

8. Under Permissions, select the Grant admin consent to openid and offline_access permissions check box.

9. Select Register.

Enable the implicit flow

If you’re using MSAL.js 1.3 or an earlier version with the implicit grant flow in your SPA app, or if you configure the https://jwt.ms/ app for testing a user flow or custom policy, you need to enable the implicit grant flow in the app registration:

1. In the left menu, under Manage, select Authentication.

2. Under Implicit grant and hybrid flows, select both the Access tokens (used for implicit flows) and ID tokens (used for implicit and hybrid flows) check boxes.

3. Select Save.

If your app uses MSAL.js 2.0 or later, don't enable implicit flow grant as MSAL.js 2.0+ supports the authorization code flow with PKCE.

Migrate from the implicit flow

If you've an existing application that uses the implicit flow, we recommend that you migrate to use the authorization code flow by using a framework that supports it, like MSAL.js 2.0+.

When all your production SPA represented by an app registration starts using the authorization code flow, disable the implicit grant flow settings as follows:

1. In the left menu, under Manage, select Authentication.
2. Under Implicit grant, deselect both the Access tokens and ID tokens check boxes.
3. Select Save.

Applications using the implicit flow can continue to function if you leave the implicit flow enabled (checked).

Next steps

Learn how to Create user flows in Azure Active Directory B2C.