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Editorial Team
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Asked: 2026-05-14T06:21:33+00:00

Can anyone tell me the difference between using mod_deflate and zlib output_compression? I understand

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Can anyone tell me the difference between using mod_deflate and zlib output_compression?

I understand that zlib is done in PHP and mod_deflate is done in Apace, my .htaccess file looks like:

php_flag zlib.output_compression On

or:

SetOutputFilter DEFLATE
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png|gif)$ no-gzip dont-vary
Header append Vary User-Agent env=!dont-vary

Advantages/disadvantages of either?

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1 Answer

  1. Editorial Team

    As far as I know they both compress the same amount as zlib.output_compression uses gzip, which is based on DEFLATE.

    PHP’s zlib output_compression will only work files passed through the PHP handler (i.e. .php files), but Apache’s mod_deflate can work on any files (eg static CSS or JS).

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