Define custom attributes in Azure Active Directory B2C

Article
11/18/2024

Before you begin, use the Choose a policy type selector at the top of this page to choose the type of policy you’re setting up. Azure Active Directory B2C offers two methods to define how users interact with your applications: through predefined user flows or through fully configurable custom policies. The steps required in this article are different for each method.

In the Add claims and customize user input using custom policies article, you learn how to use built-in user profile attributes. In this article, you enable a custom attribute in your Azure Active Directory B2C (Azure AD B2C) directory. Later, you can use the new attribute as a custom claim in user flows or custom policies simultaneously.

Your Azure AD B2C directory comes with a built-in set of attributes. However, you often need to create your own attributes to manage your specific scenario, for example when:

A customer-facing application needs to persist a loyaltyId attribute.
An identity provider has a unique user identifier, uniqueUserGUID, that must be persisted.
A custom user journey needs to persist the state of the user, migrationStatus, for other logic to operate on.

The terms extension property, custom attribute, and custom claim refer to the same thing in the context of this article. The name varies depending on the context, such as application, object, or policy.

Azure AD B2C allows you to extend the set of attributes stored on each user account. You can also read and write these attributes by using the Microsoft Graph API.

Prerequisites

Create a user flow so users can sign up and sign in to your application.
Register a web application.

Complete the steps in Get started with custom policies in Active Directory B2C. This tutorial guides you how to update custom policy files to use your Azure AD B2C tenant configuration.
Register a web application.

Create a custom attribute

Sign in to the Azure portal as at least External ID User Flow Attribute Administrator of your Azure AD B2C tenant.
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.
Choose All services in the top-left corner of the Azure portal, search for and select Azure AD B2C.
Select User attributes, and then select Add.
Provide a Name for the custom attribute (for example, "ShoeSize")
Choose a Data Type. Only String, Boolean, and Int are available.
Optionally, enter a Description for informational purposes.
Select Create.

The custom attribute is now available in the list of User attributes and for use in your user flows. A custom attribute is only created the first time it's used in any user flow, and not when you add it to the list of User attributes.

Use a custom attribute in your user flow

In your Azure AD B2C tenant, select User flows.
Select your policy (for example, "B2C_1_SignupSignin") to open it.
Select User attributes and then select the custom attribute (for example, "ShoeSize"). Select Save.
Select Application claims and then select the custom attribute.
Select Save.

Once you've created a new user using the user flow, you can use the Run user flow feature on the user flow to verify the customer experience. You should now see ShoeSize in the list of attributes collected during the sign-up journey, and see it in the token sent back to your application.

Azure AD B2C extensions app

Extension attributes can only be registered on an application object, even though they might contain data for a user. The extension attribute is attached to the application called b2c-extensions-app. Don't modify this application, as it's used by Azure AD B2C for storing user data. You can find this application under Azure AD B2C, app registrations.

Get extensions app's application ID

Sign in to the Azure portal.
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.
In the left menu, select Azure AD B2C. Or, select All services and search for and select Azure AD B2C.
Select App registrations, and then select All applications.
Select the b2c-extensions-app. Do not modify. Used by AADB2C for storing user data. application.
Copy the Application ID. Example: 00001111-aaaa-2222-bbbb-3333cccc4444.

Get extensions app's application properties

Sign in to the Azure portal.
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.
In the left menu, select Azure AD B2C. Or, select All services and search for and select Azure AD B2C.
Select App registrations, and then select All applications.
Select the b2c-extensions-app. Do not modify. Used by AADB2C for storing user data. application.
Copy the following identifiers to your clipboard and save them:
- Application ID. Example: 00001111-aaaa-2222-bbbb-3333cccc4444.
- Object ID. Example: aaaaaaaa-0000-1111-2222-bbbbbbbbbbbb.

Modify your custom policy

To enable custom attributes in your policy, provide Application ID and Application Object ID in the AAD-Common technical profile metadata. The AAD-Common* technical profile is found in the base Microsoft Entra ID technical profile, and provides support for Microsoft Entra user management. Other Microsoft Entra ID technical profiles include AAD-Common to use its configuration. Override the AAD-Common technical profile in the extension file.

Open the extensions file of your policy. For example, SocialAndLocalAccounts/TrustFrameworkExtensions.xml.
Find the ClaimsProviders element. Add a new ClaimsProvider to the ClaimsProviders element.
Insert the Application ID that you previously recorded, between the opening <Item Key="ClientId"> and closing </Item> elements.

Insert the Application ObjectID that you previously recorded, between the opening <Item Key="ApplicationObjectId"> and closing </Item> elements.

<!-- 
<ClaimsProviders> -->
  <ClaimsProvider>
    <DisplayName>Azure Active Directory</DisplayName>
    <TechnicalProfiles>
      <TechnicalProfile Id="AAD-Common">
        <Metadata>
          <!--Insert b2c-extensions-app application ID here, for example: 00001111-aaaa-2222-bbbb-3333cccc4444-->  
          <Item Key="ClientId"></Item>
          <!--Insert b2c-extensions-app application ObjectId here, for example: aaaaaaaa-0000-1111-2222-bbbbbbbbbbbb-->
          <Item Key="ApplicationObjectId"></Item>
        </Metadata>
      </TechnicalProfile>
    </TechnicalProfiles> 
  </ClaimsProvider>
<!-- 
</ClaimsProviders> -->

Upload your custom policy

Sign in to the Azure portal.
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.
Choose All services in the top-left corner of the Azure portal, and then search for and select App registrations.
Select Identity Experience Framework.
Select Upload Custom Policy, and then upload the TrustFrameworkExtensions.xml policy files that you changed.

Note

The first time the Microsoft Entra ID technical profile persists the claim to the directory, it checks whether the custom attribute exists. If it doesn't, it creates the custom attribute.

Create a custom attribute through Azure portal

The same extension attributes are shared between built-in and custom policies. When you add custom attributes via the portal experience, those attributes are registered by using the b2c-extensions-app that exists in every B2C tenant.

You can create these attributes by using the portal UI before or after you use them in your custom policies. When you create an attribute loyaltyId in the portal, you must refer to it as follows:

Name	Used in
`extension_loyaltyId`	Custom policy
`extension_<b2c-extensions-app-guid>_loyaltyId`	Microsoft Graph API

Note

When using a custom attribute in custom policies, you must prefix the claim type ID with extension_ to allow the correct data mapping to take place within the Azure AD B2C directory.

The following example demonstrates the use of custom attributes in an Azure AD B2C custom policy claim definition.

<BuildingBlocks>
  <ClaimsSchema>
    <ClaimType Id="extension_loyaltyId">
      <DisplayName>Loyalty Identification</DisplayName>
      <DataType>string</DataType>
      <UserHelpText>Your loyalty number from your membership card</UserHelpText>
      <UserInputType>TextBox</UserInputType>
    </ClaimType>
  </ClaimsSchema>
</BuildingBlocks>

The following example demonstrates the use of a custom attribute in Azure AD B2C custom policy in a technical profile, input, output, and persisted claims.

<InputClaims>
  <InputClaim ClaimTypeReferenceId="extension_loyaltyId"  />
</InputClaims>
<PersistedClaims>
  <PersistedClaim ClaimTypeReferenceId="extension_loyaltyId" />
</PersistedClaims>
<OutputClaims>
  <OutputClaim ClaimTypeReferenceId="extension_loyaltyId" />
</OutputClaims>

Manage extension attributes through Microsoft Graph

You can use Microsoft Graph to create and manage the custom attributes then set the values for a user. Extension attributes are also called directory or Microsoft Entra extensions.

Custom attributes (directory extensions) in the Microsoft Graph API are named by using the convention extension_{appId-without-hyphens}_{extensionProperty-name} where {appId-without-hyphens} is the stripped version of the appId (called Client ID on the Azure AD B2C portal) for the b2c-extensions-app with only characters 0-9 and A-Z. For example, if the appId of the b2c-extensions-app application is 11112222-bbbb-3333-cccc-4444dddd5555 and the attribute name is loyaltyId, then the custom attribute is named extension_25883231668a43a780b25685c3f874bc_loyaltyId.

Learn how to manage extension attributes in your Azure AD B2C tenant using the Microsoft Graph API.

Remove extension attribute

Unlike built-in attributes, custom attributes can be removed. The extension attributes' values can also be removed.

Important

Before you remove the custom attribute, for each account in the directory, set the extension attribute value to null. That way, you explicitly remove the extension attribute’s values. Then, continue to remove the extension attribute itself. Custom attributes can be queried using Microsoft Graph API.

Use the following steps to remove a custom attribute from a user flow in your tenant:

Sign in to the Azure portal as at least External ID User Flow Attribute Administrator of your Azure AD B2C tenant.
Make sure you're using the directory that contains your Azure AD B2C tenant:
1. Select the Directories + subscriptions icon in the portal toolbar.
2. On the Portal settings | Directories + subscriptions page, find your Azure AD B2C directory in the Directory name list, and then select Switch
Choose All services in the top-left corner of the Azure portal, search for and select Azure AD B2C.
Select User attributes, and then select the attribute you want to delete.
Select Delete, and then select Yes to confirm.

Use the Microsoft Graph API to manage the custom attributes.

Next steps

Learn how to add claims and customize user input using custom policies. This sample uses a built-in claim 'city'. To use a custom attribute, replace 'city' with your own custom attributes.