Application Initialization for IIS 7.5

Apr 21, 2015 · 4 min read


IIS Application Initialization for IIS 7.5 enables website administrators to improve the responsiveness of their Web sites by loading the Web applications before the first request arrives. By proactively loading and initializing all the dependencies such as database connections, compilation of ASP.NET code, and loading of modules, IT Professionals can ensure their Web sites are responsive at all times even if their Web sites use a custom request pipeline or if the Application Pool is recycled. While an application is being initialized, IIS can also be configured to return an alternate response such as static content as a placeholder or “splash page” until an application has completed its initialization tasks.

More information about Application Initialization can be found at


Download the extension from here. Once downloaded run the executable on the IIS server and follow the instructions, ensuring that you restart the server at the end.

Using Application Initialization

Unfortunately Application Initialization was not built into IIS 7.5, unlike IIS 8, so you do not get a nice GUI in IIS Manager. Without the GUI you have to manually edit the applicationHost.config which is found by default in the %WINDIR%\System32\inetsrv\config\ directory.

When editing the applicationHost.config file you MUST use a 64 Bit text editor, otherwise you end up with a ghost copy of your config file at %WINDIR%\SysWOW64\inetsrv\Config\ and your configuration changes will not be used. I use notepad for editing applicationHost.config.

App Pool Changes

To set the app pool to take full advantage of application initialization you need to make a few modifications. A sample default app pool is shown below.

<add name="DefaultAppPool" managedRuntimeVersion="v4.0" />

The changes you need to set the start mode of the application pool to always running. Another change that is beneficial although not strictly needed is to set the idle timeout of the application to 0, this will ensure that the application will not cool down if not used for a short while (default 20 minutes).

<add name="DefaultAppPool" managedRuntimeVersion="v4.0" startMode="AlwaysRunning">
    <processModel idleTimeout="00:00:00" />
Application Changes

In addition to application initialization, you can enable the initialization process to start whenever the application pool is started. You do so by setting the preLoadEnabled attribute in the element to “true”. For this to occur, the start mode in the element must be set to AlwaysRunning.

A default application.

<application path="/Test" applicationPool="DefaultAppPool">
    <virtualDirectory path="/" physicalPath="C:\inetpub\wwwroot\Test" />

A modified application.

<application path="/Test" applicationPool="DefaultAppPool" preloadEnabled="true">
    <virtualDirectory path="/" physicalPath="C:\inetpub\wwwroot\Test" />
Webconfig Changes

The final changes to get application initalization fully functioning is to make a webconfig change to your site. The basic configuration I use is below. The doAppInitAfterRestart setting specifies that the initialization process is initiated automatically whenever an application restart occurs.

    <applicationInitialization doAppInitAfterRestart="true">
      <add initializationPage="/" />

Testing Everything Works

The only way I have found to test that you have set application initialization set correctly up is to have a copy of your application, one were you setup application initialization and one were you do not. I then recycle both application pools, wait a short time (maybe 60 seconds), then open your browser developer tools and the network tab and hit the URL of your website and compare the time taken to get the initial response.

Using PowerShell To Speed Things Up

The steps above to setting up Application Initialization are both tedious and erroneous and you are editing potentially live configuration files by hand, this can lead to errors occurring and potentially breaking your websites. This is why I have created a couple of PowerShell scripts to set the applicationHost.config settings (you still have to set the web.config file manually).

Web Administration Module

The Web Administration Module is a PowerShell module that contains Internet Information Services (IIS) cmdlets that let you manage the configuration and run-time data of IIS. More information on this module can be found on TechNet

Update Scripts

Below are a couple of PowerShell Scripts. That automate the settings that have to be defined, as mentioned above. The scripts need to run in 64 Bit mode with PowerShell 4.

The first script sets the application pool settings and needs at the very least to have the name of the application pool passed as a parameter.

The second script sets the application settings and needs at the very least to be passed the application name passed as a parameter.

Congratulations You now know how to setup application initialization on your

IIS servers.