IIS 7.5 not compressing JSON when set in application web.config
.net, asp.net-mvc-3, iis-7.5, windows-server-2008-r2
Solution
`HttpCompression` section is defined `AppHostOnly` in `ApplicationHost.config` which prevents you from setting its properties in web.config.
The compression module reads only the server level properties from 'ApplicationHost.config' so even if you unlock the section (with `appcmd` or `overrideModeDefault="Allow"`), settings on lower level will be ignored.
Problem
I've been working on enabling JSON compression from one of our MVC3 sites. From various articles I've read it seems as though I should be able to set the `application/json; charset=utf-8` MIME type in the applications web.config file. But doing so does not enable compression. But when added to the applicationhost.config file, it works. Am I missing something here? My application web.config has the following added to it: ``` <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files"> <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" /> <dynamicTypes> <add mimeType="application/javascript; charset=utf-8" enabled="true" /> <add mimeType="application/x-javascript" enabled="true" /> <add mimeType="application/json" enabled="true" /> <add mimeType="application/json; charset=utf-8" enabled="true" /> </dynamicTypes> <staticTypes> <add mimeType="application/javascript; charset=utf-8" enabled="true" /> <add mimeType="application/x-javascript" enabled="true" /> <add mimeType="application/json" enabled="true" /> <add mimeType="application/json; charset=utf-8" enabled="true" /> </staticTypes> </httpCompression> <urlCompression doStaticCompression="true" doDynamicCompression="true" /> ``` The server is running Windows Server 2008 R2 with IIS7.5. I've also installed & enabled Dynamic Compression for the site in question. Any help would be greatly appreciated, as I do not wish to enable JSON compression for the entire server.