Question

How do I see if IIS Compression is working using Fiddler? I have a page that, when viewed through Port80Software or GID Network’s tool it appears to be coming across compressed.

However, when I watch the call in Fiddler, I see the ‘Accept-Encoding: gzip, deflate’ in the request header, but I don’t see the ‘Content-Encoding: gzip’ or ‘deflate’ in the response header. Also, in the Transformer section, ‘No Compression’ is selected.

Thanks!

Chris

Answer 1

I went straight to the source (to Eric Lawrence) and this is what he said:

Indeed, Fiddler shows your site is compressing properly.

Do you have an upstream proxy
server in your environment? Did you
try this test from your home network
rather than your corporate network?

On Microsoft’s corporate network, we
are all behind an ISA proxy server.
It’s configured to remove the outbound
Accept-Encoding header (which tells
servers to use compression) and if a
compressed response is received by the
proxy, it’s decompressed by the ISA
server. This is done so the ISA proxy
server can scan the content for
malicious data. The downside is that
Fiddler is only seeing the traffic as
it’s received from the upstream proxy.

Usually, when we need to test
compression and the like, we do so
from home or what’s called a “DTAP”—a
direct line to the internet that
doesn’t go through the proxy.