Application Pools <applicationPools>


The <applicationPools> element contains configuration settings for all application pools running on your Internet Information Services (IIS) 7 or later server. An application pool defines a group of one or more worker processes, configured with common settings that serve requests to one or more applications that are assigned to that application pool. Because application pools allow a set of Web applications to share one or more similarly configured worker processes, they provide a convenient way to isolate a set of Web applications from other Web applications on the server computer. Process boundaries separate each worker process; therefore, application problems in one application pool do not affect Web sites or applications in other application pools. Application pools significantly increase both the reliability and manageability of your Web infrastructure.

You can choose to use the default application pool provided by IIS on install, or you can create your own application pool. You can run as many application pools on your IIS 7 and later server as you need, though this can affect server performance. Application pools can contain one or more worker processes. Each worker process represents work being done for a Web site, Web application, or Web service. You can create a Web garden by enabling multiple worker processes to run in a single application pool.

In IIS 7 and later, each application pool uses one of two .NET integration modes for running ASP.NET applications: Integrated or Classic. The .NET integration mode defined for the application pool determines how IIS processes an incoming request to the sites, applications and Web services that run in that application pool.

  • Integrated mode allows IIS to process requests in the application pool by using the IIS 7 and later integrated pipeline. This allows ASP.NET modules to participate in IIS request processing regardless of the type of resource requested. Using integrated mode makes available features of the ASP.NET 2.0 request pipeline available to requests for static content, as well as ASP, PHP and other content types. By default, IIS 7 and later application pools run in this mode.
  • Classic mode uses the IIS 6.0 processing pipeline for hosting ASP.NET applications. In this mode, requests are processed initially through IIS 7 and later modules, and ASP.NET requests are further processed by the aspnet_isapi.dll. The ASP.NET processing pipeline is separate from the IIS 7 and later processing pipeline, and the ASP.NET request processing pipeline features are not available to other resource types. This also means that an ASP.NET request must pass through authentication and authorization modules in both process models. While this is not as efficient as Integrated mode, it does allow you to run applications developed using ASP.NET version 1.1 on an IIS 7 and later server without modifying the application to run in Integrated mode.

New in IIS 7.5 and later

Starting in IIS 7.5, you can configure an application to start automatically by using the managedRuntimeLoader, CLRConfigFile, and startMode attributes of the <add> element. These attributes configure, respectively, the name of the managed DLL that provides runtime loading for your application, the common language runtime configuration file for the application, and the startup type for the application.

Also new in IIS 7.5 and later is a new ApplicationPoolIdentity type for the identityType attribute of the <processModel> element. This new identity type is now the default process identity for applications, and makes it possible to set the security for your content areas to allow access for a specific application pool. To do so, you would set your security using the name of an application pool by using syntax like "IIS AppPool\DefaultAppPool." This identity is created dynamically, thereby dramatically reducing the surface attack area of your server.


Version Notes
IIS 10.0 The <applicationPools> element was not modified in IIS 10.0.
IIS 8.5 The <applicationPools> element was not modified in IIS 8.5.
IIS 8.0 The <applicationPools> element was not modified in IIS 8.0.
IIS 7.5 The <add> element of the <applicationPools> element was updated in IIS 7.5 to include attributes that allow you to preload applications by using the managedRuntimeLoader, CLRConfigFile, and startMode attributes, and to run applications using the new ApplicationPoolIdentity.
IIS 7.0 The <applicationPools> element was introduced in IIS 7.0.
IIS 6.0 The <applicationPools> element replaces the IIS 6.0 IIsApplicationPools metabase object.


The <applicationPools> collection is included in the default installation of IIS 7 and later.

How To

How to create a new application pool

  1. Open Internet Information Services (IIS) Manager:

    • If you are using Windows Server 2012 or Windows Server 2012 R2:

      • On the taskbar, click Server Manager, click Tools, and then click Internet Information Services (IIS) Manager.
    • If you are using Windows 8 or Windows 8.1:

      • Hold down the Windows key, press the letter X, and then click Control Panel.
      • Click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
    • If you are using Windows Server 2008 or Windows Server 2008 R2:

      • On the taskbar, click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
    • If you are using Windows Vista or Windows 7:

      • On the taskbar, click Start, and then click Control Panel.
      • Double-click Administrative Tools, and then double-click Internet Information Services (IIS) Manager.
  2. In the Connections pane, expand the server name, and then click Application Pools.

  3. In the Actions pane, click Add Application Pool....

  4. In the Add Application Pool dialog box, enter the name of the application pool in the Name: box, in the .NET Framework version: drop-down list select the .NET Framework version your site or application uses, in the Managed pipeline mode: drop-down list select Integrated or Classic, and then click OK.
    Screenshot of the Add Application Pool dialog box, showing the Name, dot NET Framework version, and Managed pipeline mode fields.

How to configure the application pool for an existing site or application

  1. In the Connections pane, expand Sites, and then navigate to the Web site or application you want to add to the application pool.
  2. In the Actions pane, click Advanced Settings...
  3. In the General section of the Advanced Settings dialog box, click the Application Pool entry, and then click the ellipses button.
    Screenshot of the Advanced Settings dialog box with the Application Pool entry being highlighted.
  4. In the Select Application Pool dialog box, select the application pool from the Application pool: drop-down box, click OK, and then click OK again.
    Screenshot of the Select Application Pool dialog box's Application pool field, which contains a drop-down menu of available options.


The <applicationPools> element contains a collection of <add> elements. Each element in the collection configures an application pool running on IIS 7 and later. At a minimum, each <add> element contains a name attribute that identifies the application pool to GUI and command-line management tools. The <add> element contains child elements that configure the process model, CPU, and recycling settings for the application pool.

The <applicationPools> element also contains the <applicationPoolDefaults> element, which defines default settings for all application pools on the IIS 7 and later server. To change default application pool settings across the server, you can edit the <applicationPoolDefaults> element. When you create a new application pool, the configuration settings for that application pool override the defaults set in the <applicationPoolDefaults> element.



Child Elements

Element Description
add Adds an application pool to the applicationPools section.
applicationPoolDefaults Required string attribute.

Configures the default settings for all application pools in an applicationPools section.

Configuration Sample

The following configuration sample uses the application pool <add> and <applicationPools> elements to define the standard application pools and defaults for IIS.

   <add name="DefaultAppPool" />
   <add name="Classic .NET AppPool" managedPipelineMode="Classic" />
      <processModel identityType="NetworkService" />

Sample Code

The following examples add an application pool named Contoso, and set the managed pipeline mode to Integrated.


appcmd.exe set config -section:system.applicationHost/applicationPools /+"[name='Contoso',autoStart='True',managedPipelineMode='Integrated']" /commit:apphost


You must be sure to set the commit parameter to apphost when you use AppCmd.exe to configure these settings. This commits the configuration settings to the appropriate location section in the ApplicationHost.config file.


using System;
using System.Text;
using Microsoft.Web.Administration;

internal static class Sample {

   private static void Main() {

      using(ServerManager serverManager = new ServerManager()) { 
      Configuration config = serverManager.GetApplicationHostConfiguration();

      ConfigurationSection applicationPoolsSection = config.GetSection("system.applicationHost/applicationPools");

      ConfigurationElementCollection applicationPoolsCollection = applicationPoolsSection.GetCollection();

      ConfigurationElement addElement = applicationPoolsCollection.CreateElement("add");
      addElement["name"] = @"Contoso";
      addElement["autoStart"] = true;
      addElement["managedPipelineMode"] = @"Integrated";



Imports System
Imports System.Text
Imports Microsoft.Web.Administration

Module Sample
   Sub Main()
      Dim serverManager As ServerManager = New ServerManager
      Dim config As Configuration = serverManager.GetApplicationHostConfiguration
      Dim applicationPoolsSection As ConfigurationSection = config.GetSection("system.applicationHost/applicationPools")
      Dim applicationPoolsCollection As ConfigurationElementCollection = applicationPoolsSection.GetCollection
      Dim addElement As ConfigurationElement = applicationPoolsCollection.CreateElement("add")
      addElement("name") = "Contoso"
      addElement("autoStart") = True
      addElement("managedPipelineMode") = "Integrated"
   End Sub
End Module


var adminManager = new ActiveXObject('Microsoft.ApplicationHost.WritableAdminManager');
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST";

var applicationPoolsSection = adminManager.GetAdminSection("system.applicationHost/applicationPools",

var applicationPoolsCollection = applicationPoolsSection.Collection;

var addElement = applicationPoolsCollection.CreateNewElement("add");
addElement.Properties.Item("name").Value = "Contoso";
addElement.Properties.Item("autoStart").Value = true;
addElement.Properties.Item("managedPipelineMode").Value = "Integrated";



Set adminManager = CreateObject("Microsoft.ApplicationHost.WritableAdminManager")
adminManager.CommitPath = "MACHINE/WEBROOT/APPHOST"
Set applicationPoolsSection = adminManager.GetAdminSection("system.applicationHost/applicationPools","MACHINE/WEBROOT/APPHOST")
Set applicationPoolsCollection = applicationPoolsSection.Collection

Set addElement = applicationPoolsCollection.CreateNewElement("add")
addElement.Properties.Item("name").Value = "Contoso"
addElement.Properties.Item("autoStart").Value = True
addElement.Properties.Item("managedPipelineMode").Value = "Integrated"