Issue: Visual Studio 2012 > “Unable to launch the IIS Express Web Server”

Steps to Problem/Issue

  • I installed Visual Studio 2012 RTM.
  • Created an MVC 4 project template in Visual Studio 2012
  • Without any code changes, I hit F5 debug.
  • Issue: I get a pop up message “Unable to launch the IIS Express Web Serve

After much searching and many suggest re-install Visual Studio 2012, but it takes a long time (>20 mins) and I’m pretty stubborn at times to find root cause.

I found myself looking at the applicationhost.config file located at

Look for <applicationPools> node.

I updated managedRuntimeVersion=”4.0″ to “4.0.30319”

<add name=”Clr4IntegratedAppPool” managedRuntimeVersion=”v4.0.30319″ managedPipelineMode=”Integrated”     CLRConfigFile=”%IIS_USER_HOME%\config\aspnet.config” autoStart=”true” />

Back to Visual Studio 2012 Project Solution, I hit F5 Debug and IE loaded with the App!

Roy Kim

19 thoughts on “Issue: Visual Studio 2012 > “Unable to launch the IIS Express Web Server”

  1. Pingback: IIS Express | solinate

  2. Dennis

    I updated a lot of stuff through Windows Update yesterday, something must have tampered with VS. Worked for me too, thank you so much!

  3. Hello friends, I want to share with you where I originally indicated in the example and I worked, what I did was uninstall IIS 8 Express, physically remove IIS Express folders in Documents and reinstall IIS again and it worked properly.

  4. otog

    changed it per ur instructions then changed it back to v4.0 and it worked fine. hmmmmmmm. hmmmmmm. hmmmmmm. i just love typing hmmmmmmm.

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