Azure Web Apps has a unique subdomain. It is azurewebsites.net. For development, QA, and stage, we can manage with a unique subdomain, but for the production application, it is essential to have a custom domain.
We can map a custom domain to the Azure web application using Azure portal. By default, the name of Azure web app will be <webapp_name>.azurewebsites.net. To map a custom domain, go to Azure web application in the Azure portal, go to SETTINGS and click on Custom domains.
We can purchase domains and add a hostname too: