Unable to launch the IIS Express Web server error on Visual Studio 2015 – How to fix it

Working with Visual Studio on recent Windows versions such as Windows 10 can be tricky, as the improved security settings of the new OS might create some issues on a developer machine, which often need to have access to some system files – expecially when working with IIS Express. We talked about that in a number of post, for example here (error accessing IIS Metabase), here (allow external requests from remote machines) and also here (Process with an ID #### error).

Here we’ll introduce another issue you might stumble upon while working with an ASP.NET Core or MVC solution, right after you try to execute it in debug mode:

Unable to launch the IIS Express Web server

There are many workaround that might fix this issue: we suggest to try them one after another, stopping only when you manage to fix it.

1. Delete the \Documents\IISExpress folder using the following console command:

   rmdir /s /q "%userprofile%\Documents\IISExpress"

2. Delete the applicationhost.config file which is placed within the \.vs\Config\ folder in your Visual Studio project root folder.
3. Close Visual Studio and re-start it with Administrative priviledges (right-click > Run as Administrator).
4. Change the project’s website random URL: within Visual Studio, right-click to the project node in Solution Explorer, then select Properties; navigate through the Web panel, then change the number in the Project Url textbox value.
5. Add the _CSRUN_DISABLE_WORKAROUNDS Environment System variable with the value of 1 as shown in the following screenshot (thanks to Juan M. Elosegui for reporting this on this SO thread and for the image):

In case you manage to fix the issue, let us know which of the given workarounds worked for you by leaving a feedback in this post’s comment section.

That’s it for now: happy coding!

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