test IIS compression using fiddler

[Jenny]

Hi there,

I am trying to verify if IIS compression is working, I read on line
that I could use fiddler to verify, but I couldn't found a way to do
so, can anyone help?

Here is what I did so far:

1. turn on IIS compression in IIS manager.
2. hit URL http://<server_name>/<site_name>, check the request headers
in the "Inspectors" tab, I was expecting to see "Content-Encoding:
gzip" but I did not see it.
3. If I manually check "GZIP Encoding" on the "Transformer" tab and go
back to "headers" tab, I will see "Content-Encoding: gzip".

At this moment I am sure this is not the right way to verify IIS
compression, since I see the same behavior even before I turned on IIS
compression. Can anyone let me know how to verify IIS compression
using fiddler?

Thanks,
Jenny

[EricLaw]

If the "Transformer" response inspector does not show that the content
is encoded with GZIP or DEFLATE, then generally speaking that means
that the server hasn't compressed that response.

This could occur for any number of reasons:

1> Some servers will not compress their first response for a given
file; they serve the first response uncompressed and compress the
response in parallel and cache it for the next request
2> You may have a proxy between you and the server which is
decompressing the response.
3> You may have client software (e.g. certain security software of
dubious quality) which is stripping out the request's Accept-Encoding
header.
4> You may be looking at a file type which IIS typically will not
compress (e.g. an image)

Also possible:
5> You may have enabled (or written) a rule in Fiddler which is
automatically decompressing the response (e.g. the AutoDecode toolbar
button).

-Eric