IIS7 StaticContent and ClientCache Settings

Submitted on Jun 12, 2009, 5:58 p.m.

Yet another great feature of IIS7  - declarative static content cache settings. It took a little detective work to find the settings for this feature – including a helpful post from Jörg Jooss.

I wanted to be able to set the client cache settings for the static content of a site I host at ORCS Web. In the past – unless offered by the control panel of your shared hosting provider – this would have meant emailing support and asking them to set the client cache header settings for the required directory in IIS6. In IIS7 this can be set now in the <system.webserver> section.

Note: If you’re going to try this on your local machine first, you will need to unlock the staticContent section in IIS7 (from the machine level) using the following appcmd…

1appcmd unlock config /section:staticContent

You can also use appcmd to create the static content cache settings as shown in Jörg’s post above, which will add the correct section to your web.config – or you can directly edit/create the web.config file for the required directory.

I chose to hand edit the web.config – creating a new web.config located in the directory with the static content (i.e. images, style sheets, script files – all under the ‘assets’ directory in my case)

1<?xml version="1.0"?>
2<configuration>
3 <system.webServer>
4 <staticContent>
5 <clientCache cacheControlCustom="private" cacheControlMode="UseMaxAge" cacheControlMaxAge="3.00:00:00" />
6 </staticContent>
7 </system.webServer>
8</configuration>

A couple of things to note about these settings. Firstly – you can add any custom cache control header setting using the cacheControlCustom attribute (e.g. no-store, must-revalidate, private, public etc). Secondly using the http 1.1 max-age setting – you can specify days – by using the 1.00 notation for the hours portion of the hh:mm:ss timespan value. So the setting above will set the max-age value to 3 days – or 259200 seconds when you see it in the response header.