Can't start IIS 10 Express


I can't start IIS Express 10 with .NET Core since yesterday. Nothing changed outside of a NET Framework 3.5 and 4.8 Update.

I tried restarting Machine, restarting VS, reinstalling IIS Express, the port is not occupied by any other process. In fact when I change the port the app is running on I still get the error, I get the error no matter the port I use. I removed the .vs folders and IIS Express folders. I also reset the network adapters and started shutting down applications one by one (which anyway actually didn't make sense because no matter which port I change it to, the error stays as mentioned.)

The error that I am getting when I check the logs:

Failed to register URL "http://localhost:50721/" for site "Application" application "/". Error description: The process cannot access the file because it is being used by another process. (0x80070020)

I checked the other posts and nothing works, I am using VS2019.

Any idea?

asked on Stack Overflow Dec 12, 2019 by qubits • edited Dec 15, 2019 by qubits

2 Answers


As far as I know, this error means binding conflict. There is another application that is using port 50721.
I suggest you could open your task manager and end the IIS express task. Then you could right click the project and click properties, then click the web tag and modify the project url's port to another one.

answered on Stack Overflow Dec 13, 2019 by Brando Zhang

Try going into the Visual Studio Installer and uninstall-reinstall the ASP.NET dev components. Sometimes you have to start all over again to make dev tools work with updates on client builds.

answered on Stack Overflow Dec 19, 2019 by fdrobidoux

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