Custom Domain Mapping Process Flow

Before mapping a custom domain to an Azure App Service, the administrator must prove ownership of the domain through a verification step. This requires the App Service app to be running on a tier above the Free tier. The process begins by navigating to the App Service in the Azure portal, opening the Custom domains pane, and copying the Custom Domain Verification ID—a unique string that ties the domain to the Azure resource. On the domain provider’s DNS management page, a TXT record is added with a host name that depends on the target domain type. For a root domain such as contoso.com, the host is _asuid and the value is the copied verification ID. This TXT record proves that the administrator controls the DNS zone and prevents unauthorized binding.