Running 32-bit or 64-bit IIS Express

IIS Express runs x86 / 32-bit as standard, but there is also a 64-bit version.


The version used for all web projects can be configured in Visual Studio 2013 or 2015 in the Tools -> Options… dialog.

Under: Project and Solutions -> Web Projects

The setting is:  Use the 64 bit version of IIS Express for web sites and projects



I encountered this while trying to debug some startup and initialization issues with IIS Express and Visual Studio.

The result from:


Was the path: C:\Program Files (x86)

But I was expecting the path: C:\Program Files

This was a clear sign that IIS Express was running as x86 / 32-bit.


Found the Visual Studio setting here:

Other possible solutions are to modify the registry or calling the desired version of IIS Express with a script.