GZip Compression On IIS 7.5 is not working

After a lot of searching, I finally found what got compression working on my IIS 7.5.
To start with, IIS will not compress a file unless it loaded often enough. That brings up the question “what does IIS consider often enough?” Well, the defaults are 2 times every 10 seconds. Yikes!

This setting can be changed in web.config, but the section needs to be unlocked first in applicationHost.config. Here are the commands:

First unlock the section:

C:\Windows\System32\inetsrv\appcmd.exe unlock config
/section:system.webServer/serverRuntime

Unlocked section “system.webServer/serverRuntime” at configuration path “MACHINE/WEBROOT/APPHOST”.

Now that is done, edit the web.config file and add the serverRuntime element:

<?xml version=”1.0″ encoding=”UTF-8″?>
  <configuration>
    <system.webServer>
      <serverRuntime frequentHitThreshold=”1″ frequentHitTimePeriod=”10:00:00″ />

In this case, I set it to hit the file once in a 10 hour period. You can adjust the values as necessary. Here is the document that explains the serverRuntime element:

http://www.iis.net/configreference/system.webserver/serverruntime

I hope this helps get your compression working as well.

Note: you can also set the serverRuntime element up in the applicationHost.config file, but I chose to change it in the web.config because we have a number of servers and farms with various sites, and it is easier for me to control it from this level of granularity.

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