Why is gzip compression with Internet Explorer not working?

Question

My site is gzipped compressed, and it doesn't load properly in IE. It works fine in FF/Chrome, but in IE, the only thing that pops up is a box asking to download the .gz file which contains the html document for the page.

Is this normal? Do I have to turn off gzip?

Answer 1

Are you sending the correct headers?

You need to send the

Content-Encoding: gzip

header for IE to understand that it is gzipped (Firefox, et al are smart enough to detect this automatically - even though they shouldn't!)

In PHP, you can do this using:-

header('Content-Encoding: gzip');

Answer 2

One thing to add - you should turn off gzip compression for IE6 pre-SP2. Before SP2, IE6 doesn't always read and cache gzipped content properly and you end up with mangled code.

You can identify an IE6 SP2 install by looking for "SV1" in the user-agent string.