Compressing but no Compression

MiscellaneousUser

6/18/24, 12:53 AM

Ok, on IIS i have GZip and Brotli installed, I changed the priority of the two around. The headers are now showing "Content-Encoding : GZIP" but when I use tools.pingdom.com , it is saying there's no compression.

I have the following in applicationhost.config

    <httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files" minFileSizeForComp="0">
        <scheme name="gzip" dll="%ProgramFiles%\IIS\IIS Compression\iiszlib.dll" />
        <scheme name="br" dll="%ProgramFiles%\IIS\IIS Compression\iisbrotli.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="image/svg+xml" 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="*/*" enabled="false" />
        </dynamicTypes>
    </httpCompression>

I have the following in Web.config

<httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files" dynamicCompressionBufferLimit="1200000">
  <remove name="br"/>
  <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" staticCompressionLevel="9" dynamicCompressionLevel="6" doDynamicCompression="true" doStaticCompression="true" />
  <dynamicTypes>
    <add mimeType="text/*" enabled="true" />
    <add mimeType="message/*" enabled="true" />
    <add mimeType="application/javascript" enabled="true" />
    <add mimeType="*/*" enabled="false" />
  </dynamicTypes>
  <staticTypes>
    <add mimeType="text/*" enabled="true" />
    <add mimeType="message/*" enabled="true" />
    <add mimeType="application/javascript" enabled="true" />
    <add mimeType="*/*" enabled="false" />
  </staticTypes>
</httpCompression>

Do I need to uninstall the Brotli version and see if GZIp works or is there something else I'm missing thats preventing GZIP from working?

0 + 3

iis

gzip

Lex Li

6/18/24, 6:04 AM

https://learn.microsoft.com/en-us/iis/troubleshoot/performance-issues/troubleshooting-iis-compression-issues-in-iis6-iis7x You should learn that IIS won't compress a response in many cases.

Greg Askew

6/18/24, 8:04 AM

What does your packet capture show?

MiscellaneousUser

6/18/24, 9:35 AM

What do you mean? I check the headers via Fiddler, they say Content-Encoding:GZIP but the size of the file is the same as it is uncompressed. When I check https://www.whatsmyip.org/http-compression-test/ it says I have 0.1 compression. The file is big enough to be compressed -> 50 Kb

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Compressing but no Compression

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