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InfoQ Homepage News Microsoft Announces IIS Express – A New Built-In Web Server for Visual Studio

Microsoft Announces IIS Express – A New Built-In Web Server for Visual Studio

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Scott Guthrie recently announced IIS Express, a light weight alternative to IIS and a potential replacement of Cassini (the built in web server for Visual Studio). IIS Express is intended to solve the pain points reported in Cassini and enable developers to develop using a full IIS 7.x feature-set. It’s not available for download yet, but according to Scott should be available shortly.

IIS Express works in the same way as Cassini by starting up when debugging or running the application. Its supported on Windows XP or higher, does not require and administrator account, support classic ASP, PHP, SSL, URL Rewrite, Media and other file-types and extensions supported by IIS. As for SSL support a self-signed certificate is automatically installed on startup.

The express edition will be supported in Visual Studio 2010 and Visual Web Developer 2010 Express after installing a patch for Visual Studio 2010, and will be included in future versions of Visual Studio. It can however be run from command line allowing earlier versions of Visual Studio to use it as well:

You will be able to use it with VS 2008 if you launch it from the command-line.  We won't have integrated tooling support for it except with VS 2010.

Scott responds to one of his readers with the complete usage and examples of the command line version:


iisexpress [/config:config-file] [/site:site-name] [/systray:boolean]

iisexpress /path:app-path [/port:port-number] [/clr:clr-version] [/systray:boolean]


The full path to the applicationhost.config file. The default value is the IISExpress8\config\applicationhost.config file that is located in the user's Documents folder.


The name of the site to launch, as described in the applicationhost.config file.


The full physical path of the application to run. You cannot combine this option with the /config and related options.


The port to which the application will bind. The default value is 8080. You must also specify the /path option.


The .NET Framework version (e.g. v2.0) to use to run the application. The default value is v4.0. You must also specify the /path option.


Enables or disables the system tray application. The default value is true.


iisexpress /site:WebSite1

This command runs WebSite1 site from the user profile configuration file.

iisexpress /config:c:\myconfig\applicationhost.config

This command runs the first site in the specified configuration file.

iisexpress /path:c:\myapp\ /port:80 

This command runs the site from c:\myapp folder over port 80.

One of the limitations with Cassini is that it’s only accessible from localhost, but in response to one of his readers Scott says IIS Express can be modified to allow remote requests.

Another reader asked about connection limits and redistribution:

…you can redistribute IIS Express with your applications.  There are no connection limits.

To questions about Azure integration, SharePoint and Edit and Continue support, Scott responded:

We don't have Azure/IIS Express integration just yet.  It is something we are planning to look at for the future though.

…unfortunately we don't support SharePoint with IIS Express.  You need the full IIS for that.

…edit and Continue isn't supported just yet - but is something we are looking at.

He also provided some more information about the differences between IIS and IIS Express:

The core code is the same across both.  The main difference is that IIS Express launches its worker process from the command-line or from VS (or another tool). The full IIS has an on-demand worker process model and activation system and can bring up and shutdown worker processes on demand.

Scott also mentions that IIS Express is one of several components they are going to release shortly and he will announce several others leading up to the release.

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