Philadelphia Reflections

The musings of a physician who has served the community for over six decades

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Server-Side gzip Compression

Compression can reduce the size of the text (not images) of your web pages as they are transmitted outbound to the client. This will have only a small impact on response time over modern fiber connections but it will significantly reduce your bandwidth consumption (70% on average on this site.)

In XHTML vs. HTML I show how I implemented gzip compression on this site. The problem with that method is that it's a pain. Soon another website, I tried out the Apache access method to instruct the server to compress all outbound pages. Works like a charm.


# See https://httpd.apache.org/docs/2.0/mod/mod_deflate.html

# Insert filter
SetOutputFilter DEFLATE

# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip

# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won't work. You can use the following
# workaround to get the desired effect:
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html

# Don't compress images
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png)$ no-gzip dont-vary

# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary

Originally published: Monday, February 11, 2008; most-recently modified: Wednesday, June 05, 2019