I have a demo DNN website that I'm using to test service framework.  The site is hosted on IIS 8.5.  I have enabled dynamic content compression on the server and compression is working fine when accessing the site.  However, when I access my service WebAPI compression is not working.  I have modified (C:\Windows\System32\inetsrv\config\applicationHost.config) as suggested on other forums to have the following:

        <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files">

            <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" />

            <staticTypes>

                <add mimeType="text/*" enabled="true" />

                <add mimeType="message/*" enabled="true" />

                <add mimeType="application/javascript" enabled="true" />

                <add mimeType="application/atom+xml" enabled="true" />

                <add mimeType="application/xaml+xml" enabled="true" />

<add mimeType="application/json" enabled="true" />

<add mimeType="application/xml; charset=utf-8" enabled="true" />

<add mimeType="application/json; charset=utf-8" enabled="true" />       

                <!-- <add mimeType="*/*" enabled="false" />  -->

            </staticTypes>

            <dynamicTypes>

                <add mimeType="text/*" enabled="true" />

                <add mimeType="message/*" enabled="true" />

                <add mimeType="application/x-javascript" enabled="true" />

                <add mimeType="application/javascript" enabled="true" />

<add mimeType="application/json" enabled="true" />

<add mimeType="application/xml; charset=utf-8" enabled="true" />

<add mimeType="application/json; charset=utf-8" enabled="true" />       

<!-- <add mimeType="*/*" enabled="false" /> -->

            </dynamicTypes>

        </httpCompression>

and restarted IIS after modifying the file without success.

 http://54.174.210.20/lilypad/ ----->> is compressed

but not http://54.174.210.20/lilypad/desktopmodules/DataExchange/API/Example/GetData

Am I missing something?

Thank you for the respond.  I actually did use Fiddler and Google Developer Tools to track the request and response.  In summary, when only accessing the Lilypad homepage (Plain DNN main page), I get the following response headers:

HTTP/1.1 200 OK

Cache-Control: private

Content-Type: text/html; charset=utf-8

Content-Encoding: gzip

Vary: Accept-Encoding

Server: Microsoft-IIS/8.5

Set-Cookie: dnn_IsMobile=False; path=/; HttpOnly

Set-Cookie: language=en-US; path=/; HttpOnly

Set-Cookie: dnn_IsMobile=False; path=/; HttpOnly

Set-Cookie: language=en-US; path=/; HttpOnly

Date: Fri, 19 Dec 2014 03:49:21 GMT

Content-Length: 7540 

----

Yet, when I access the WebAPI module, I get the following:

HTTP/1.1 200 OK

Cache-Control: no-cache

Pragma: no-cache

Content-Type: application/xml; charset=utf-8

Expires: -1

Server: Microsoft-IIS/8.5

Set-Cookie: dnn_IsMobile=False; path=/; HttpOnly

Set-Cookie: dnn_IsMobile=False; path=/; HttpOnly

Set-Cookie: language=en-US; path=/; HttpOnly

Date: Fri, 19 Dec 2014 03:50:14 GMT

Content-Length: 3187900

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As you can see, the exact Content-Type  in the second response headers has been added to the MIME type for the dynamic compression.