Help Required with App service create

Question

I deleted an Azure App Service named A276862484005test more than two weeks ago in Tenant A. I need to recreate the exact same name in Tenant B. The name is still showing as unavailable globally (AlreadyExists). Please release the backend hostname reservation for this app service name.

Answer 1

Hi @Shreeraksha G
Azure App Service default names (like A276862484005test.azurewebsites.net) must be globally unique across all tenants and subscriptions, and when an App Service is deleted, Azure does not always release the hostname immediately. Instead, deleted apps can remain in a soft-deleted or reservation state for up to ~30 days to help prevent subdomain takeover. During this retention period the hostname can still show as AlreadyExists, even if the resource was deleted and even if you try in a different tenant. Microsoft’s official documentation confirms that deleted App Services can be restored within a retention window and that the hostname isn’t immediately freed.
You can verify whether the app still exists in a soft-deleted state by checking Azure Portal / App Services / Manage Deleted Apps or by running az webapp deleted list in Azure CLI. If the app appears there, you can restore or permanently delete (purge) it; if it does not appear and the name remains unavailable beyond the retention period
https://learn.microsoft.com/en-us/azure/app-service/app-service-undelete
Let me know if you have any further assistances needed.

Answer 2

Hello Shreeraksha G,

The AlreadyExists error you are encountering when moving an App Service between tenants is an intended security mechanism known as Subdomain Takeover Protection (or anti-dangling DNS protection).

When you delete an Azure App Service, the corresponding backend DNS (e.g., <app-name>.azurewebsites.net) is explicitly forbidden from reuse by any subscription outside of the original tenant. This gives the original owner time to clean up external DNS CNAMEs without the risk of a bad actor instantly hijacking the traffic.

While the security documentation states this gives you "some time", the exact duration of this block is dictated by the App Service Soft-Delete lifecycle. Deleted apps are held in a soft-delete state for exactly 30 days before they are permanently purged, at which point the FQDN is released to the global pool.

To ensure you don't have other vulnerable records pointing to deleted resources, Microsoft provides a GitHub-hosted PowerShell tool called Get-DanglingDnsRecords.

• This tool scans your Azure resources and lists domains with a CNAME associated with Azure services.
• It supports scanning various resources including Azure App Service, Front Door, Blob Storage, and API Management.

Official Documentation References:

Prevent Subdomain Takeovers - Azure App Service

Restore deleted apps in Azure App Service (30-day rule)

Identify dangling DNS entries

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