When you configure a custom domain (like www.contoso.com) for an Azure Web App (App Service), Azure requires that the domain be verified to ensure ownership before binding it to the app.
According to Microsoft Azure official documentation (“Map a custom domain name to your Azure web app” — Microsoft Learn):
“Before you can add a custom domain, you must verify that you own the domain name by creating a DNS record with your domain registrar. Azure uses an asuid verification record, which can be either a CNAME or TXT record, depending on your DNS provider.”
The first step is to create a CNAME or TXT record in your DNS zone that links your custom domain to the Azure verification ID.
The record name is asuid.contoso.com.
The value (target) is the domain verification ID shown in the Azure portal under Custom domains → Custom hostnames → Domain ownership.
Once Azure verifies the domain ownership using that record, you can add www.contoso.com as a custom hostname in the web app configuration.
✅ Key Point:
Step 1: Verify domain ownership using a CNAME or TXT record.
Step 2: Bind the custom hostname (www.contoso.com) to your web app.
Thus, the correct and verified answer is:
✅ A. Create a CNAME record named asuid that contains the domain verification ID.
