You can use the Azure App Service Migration Assistant directly from the Azure Migrate hub. This tool can help you assess and migrate your on-premises web apps to Azure. 

It offers the following features:

• Assess web apps online: You can assess on-premises websites for migration to Azure App Services using the App Service Migration Assistant. 
• Migrate web apps: Using the Azure App Service Migration Assistant, you can migrate .NET and PHP web apps to Azure.

The assessment process starts by providing a public endpoint that is scanned to provide a detailed list specifying the different technologies that are used. These technologies are then compared to other sites that are hosted on Azure App Service to generate an accurate assessment report for your site.