Web Servers in Visual Web Developer

This topic describes using either Internet Information Services (IIS) or the built-in ASP.NET Development Server for testing and running Web sites.

To test or run ASP.NET Web applications, you need a Web server. The production Web server for Microsoft operating systems is IIS, which includes a Web server, File Transfer Protocol (FTP) server, Simple Mail Transfer Protocol (SMTP) virtual e-mail server, and other facilities. In order to run IIS, you must be working with a version of Windows that is designed to function as a server in a network environment. This includes the Web Edition of Windows Server 2003.

In Windows 2000 Server and previous versions of Windows server operating systems, IIS is installed by default as part of the operating system. In Windows XP and Windows Server 2003, IIS is not installed by default; you can add it using the Add/Remove Windows Components option of Add or Remove Programs in Control Panel. (In Windows Server 2003, you can install IIS using the Application Server component.)

It might be impractical for you to work with IIS for reasons such as the following:

  • You are developing ASP.NET Web pages while working with Windows XP Home Edition, which does not support IIS.

  • You do not want to host a Web server on your computer (for example, on your home network) for security reasons. Running a Web server such as IIS requires that you perform extra steps to help secure the server and that you are vigilant about installing the latest security updates.

  • Corporate policy does not allow you to install certain server components such as IIS.

For more information about working with IIS, see the following topics:

The ASP.NET Development Server

If you cannot or do not want to use IIS as your Web server, you can still test your ASP.NET pages by using the ASP.NET Development Server. The ASP.NET Development Server, which is included with Visual Web Developer, is a Web server that runs locally on Windows operating systems, including Windows XP Home Edition. It is specifically built to serve, or run, ASP.NET Web pages under the local host scenario (browsing from the same computer as the Web server). In other words, the ASP.NET Development Server will serve pages to browser requests on the local computer. It will not serve pages to another computer. Additionally, it will not serve files that are outside of the application scope. The ASP.NET Development Server provides an efficient way to test pages locally before you publish the pages to a production server running IIS.

The ASP.NET Development Server only accepts authenticated requests on the local computer. This requires that the server can support NTLM or Basic authentication.


As a best practice, do not run Visual Web Developer while you are logged on as an Administrator — run it under a more restrictive account. This helps prevent inadvertent access to other files on the server.

The ASP.NET Development Server works only with individual pages and does not include the extra facilities of IIS. For example, the ASP.NET Development Server does not support an SMTP mail server. If your Web application involves sending e-mail messages, you must have access to the IIS SMTP virtual server to test e-mail because the ASP.NET Development Server cannot forward e-mail messages or invoke a server that does.

Running the ASP.NET Development Server

The ASP.NET Development Server is installed by default with Visual Web Developer. If you are working with a file-system Web site, Visual Web Developer automatically uses the ASP.NET Development Server to run pages. By default, the Web server is invoked on a randomly selected port for the local host scenario. For example, if you are testing a page called ExamplePage.aspx, when you run it on the ASP.NET Development Server, the URL of the page might be:


When you close the browser, the ASP.NET Development Server shuts down again.

If you want to run the ASP.NET Development Server on a specific port, you can configure the server to do so. You might do this in these scenarios:

  • If code in your application listens to a specific port and you want to be able to test the application using the ASP.NET Development Server.

  • If your application includes a reference to a client project or Web service that is bound to a specific port.

Visual Web Developer cannot guarantee that the port you specify will be available when you run your file-system Web site. For details, see How to: Specify a Port for the ASP.NET Development Server.

Security Context for the ASP.NET Development Server

An important difference between the ASP.NET Development Server and IIS is the security context in which the respective servers run your ASP.NET pages. This difference can affect your testing because of differences in how the pages run.

When you run a page using the ASP.NET Development Server, the page runs in the context of your current user account. For example, if you are running as an administrator-level user, a page running in the ASP.NET Development Server will have administrator-level privileges. In contrast, in IIS, by default ASP.NET runs in an account that has limited privileges. For more information, see Application Pool Identities on the IIS.net Web site.

If you are simply reading and running the code in ASP.NET pages, this difference is not very important. However, the different security contexts for the two Web servers can affect your testing of the following:

  • Access to other resources that the page requires   This can include reading and writing files other than Web pages, reading and writing the Windows registry, and so on.

  • Database access   When working with the ASP.NET Development Server, you can typically rely on Windows Integrated authentication to access SQL Server. However, when the same page runs in IIS under the ASPNET, NETWORK SERVICES, or appPoolIdentity account, the page is running in the context of a local user. In these cases you can add NETWORK SERVICES or appPoolIdentity as a SQL Server login. For details, see Accessing SQL Server from a Web Application and ASP.NET Security Architecture.

  • Code access security   If your page involves access to resources that are protected under different zones, the page might run differently under the ASP.NET Development Server and IIS.

  • Access to other resources that the page requires   This can include reading and writing files other than Web pages, reading and writing the Windows registry, and so on.

Even though you can use the ASP.NET Development Server to test that pages are functional, you should test them again after publishing the pages to a production Web server that is running IIS.

File Authorization on the ASP.NET Development Server

In a file-system Web site, static files, such as images and style sheets, are subject to ASP.NET authorization. For example, static files in a file-system Web site will not be served to an anonymous user when anonymous access to those files is disabled. However, when you create a Web site project in an HTTP location, IIS serves static files without using authorization rules.

See Also


Walkthrough: Creating a Basic Web Page in Visual Web Developer


File System Web Sites

Change History




May, 2011

Added link to information about Application Pool identities.

Customer feedback.

April 2009

Added links to IIS documentation.

Customer feedback.