Using Fiddler to check IIS Compression

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 compre

Answer 1

Based on the various answers and comments, I'm going to conclude that perhaps the page itself (text/html) is compressed, but the text/xml you deliver as part of an AJAX request(?) and the other content delivered for the page is not.

As I already mentioned in a comment, you typically want to compress text/* (i.e. - text/html, text/plain, text/css, etc) and application/javascript & application/ecmascript (as per rfc4329). If you deliver your .js files using some other MIME type (for example, application/x-javascript or text/javascript), compress that instead, or change the MIME type used to deliver .js files to the RFC standard.

See the appropriate link below for updating the MIME types being compressed on your server:

• Using HTTP Compression On Your IIS 5.0 Web Site
• Customizing the File Types IIS Compresses (IIS 6.0)
• How to add content types for HTTP compression in IIS 7.0

One last point I should make, some web browsers (in particular certain versions of Netscape 4 but there may be others) send Accept-Encoding: gzip,deflate for CSS and JavaScript file requests, but could not actually decompress the content. Also, some versions of Internet Explorer (5.5 & 6) had problems with compression.

I know the default Apache compression configuration I used deals with these issues, I'm not sure how (or whether) IIS compensates for them.