How Can I Determine if HTTP Requests/Responses are compressed in IE7?

Question

I'm trying to use Fiddler (v2.2.2.0) to see if HTTP traffic through IE7 is being compressed. I'm not seeing Accept-Encoding or Content-Encoding request/response headers being sent/returned and I do not need to decode the response data once it's arrived, which leads me to believe that the responses are NOT coming back compressed.

However, when making the same requests using FireFox 3.5.7, I could see through FireBug that FF was sending Accept-Encoding and YSlow at least thought my data was coming back compressed.

A comment in this question:

http://stackoverflow.com/questions/897989/using-fiddler-to-check-iis-compression

suggested that a proxy server may be to blame for stripping out headers and decompressing the content for security reasons. I am using Verizon FIOS for my broadband at home and am now wondering if Verizon is proxying my HTTP traffic?

In short, how can I positively confirm/deny that responses are coming back compressed through IE?

Thanks.

Answer 1

Fiddler sees your request before any upstream proxy has the ability to mess with it. So, if you don't see an Accept-Encoding being sent from IE, there are three possibilities:

1. You have the Rules > Remove All Encodings option checked in Fiddler.

2. You have either of the "Use HTTP/1.1" checkboxes unchecked iside Tools > Internet Options > Advanced in IE.

3. You have a piece of security/privacy/filtering software or addons (e.g. Norton/SpyBot/etc) installed and have it intercepting and stripping compression from IE.