IIS7 Web.Config Caching - what are the differences here, and how does it all come together?

Question

In IIS7 I've got the ability to set caching options. These options are added to my web.config as such...

    <caching maxCacheSize="262144">
        <profiles>
            <add extension=".png" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".jpeg" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".jpg" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".css" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".js" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
        </profiles>
    </caching>

However, I've also got the following for "caching"

    <staticContent>
        <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="90.00:00:00" />
        <remove fileExtension=".js" />
        <mimeMap fileExtension=".js" mimeType="text/javascript" />
    </staticContent>

What are the differences between these two configs? They are both nested in the <system.webServer> tag, so they're both valid for IIS7.

Also, what is the right approach when using these? I currently only use this is my static assets folder. I don't use this caching on anything else.

Thanks in advance.

Markowitz

Chase, were you able to find out anymore information on this? StaticContent seems to be mucking with my caching profiles and I'm curious about any information that could be shared. – Kissiah

After I asked, I sorta forgot about it. I would like a good canonical answer. – Markowitz

Answer 1

The main difference is that

• the first is for server-side caching of dynamic output such as aspx pages (basically keeps the page output in memory for subsequent requests). As @artem-vertiy's answer points out, using it for static content makes no sense.

• the second one is 'internet-side' : it is implemented by writing standard response headers, it tells both client browsers and public proxies how to manage cached files.

Harrold

If you specify location="ServerAndClient" in the add extension=".png" tag, you can cache on the client as well as the server – Staffard

Answer 2

I've noticed that people often confuse the things above and write articles where recommend things as in the first block, i.e. output caching for static resources

Output caching:

Output caching is unnecessary for static files, such as HTML, JPG, or GIF files, and can cause more memory overhead for dynamic ASP.NET or PHP pages that read from a database that changes frequently

Thus

<add extension=".png" ../>
<add extension=".jpeg" ../>
etc.

is useless at least when you don't have ashx http handler for .png or .jpeg etc.

Magallanes