How to Delete a SharePoint Web Application

SharePoint Web Applications are actually an IIS Containers at top level. Each web application we create from SharePoint, creates respective site in IIS and a content database in SQL Server.

To delete a SharePoint 2016 Web Application,

• Open SharePoint 2016 Central Administration Site
• Click on "Manage web applications" link under "Application Management"
• Select your target web application, and from the ribbon, click on Delete button.
• Specify whether you would like to delete the content databases and IIS web sites.
  
• Confirm the Prompt once to delete a web application in SharePoint 2013 and your web application will be deleted momentarily.

This removes the specified web application from the SharePoint farm.

SharePoint delete web application zone:
To delete SharePoint web application extension, From SharePoint Central Administration:

• Click on Administration Management >> Manage Web Applications
• Select the web application you wish to remove the extended zone from >> Click on Delete button drop-down and choose "Remove SharePoint from IIS Web Site"
• Select IIS web site & zone to remove, (make sure its not your "Default" zone!)
• Set the value for "Delete IIS web sites" to "Yes" and click OK to delete web application zone.

To delete a SharePoint web application using PowerShell, use this script: Delete SharePoint web application using PowerShell