Apache HTTP Server Version 2.0

Apache > HTTP Server > Documentation > Version 2.0 > Modules

# Apache Module mod_deflate

Description: | Compress content before it is delivered to the client
Status: | Extension
Module Identifier: | deflate_module
Source File: | mod_deflate.c

### Summary

The `mod_deflate` module provides the `DEFLATE` output filter that allows output from your server to be compressed before being sent to the client over the network.

### Directives

### Topics

- Enabling Compression

### See also

- `AddOutputFilter`
- `SetOutputFilter`

## Enabling Compression

Compression is implemented by the `DEFLATE` filter. The following directive will enable compression for documents in the container where it is placed:

Most popular browsers can not handle compression of all content so you may want to set the 'gzip-only-text/html' note to 1 to only allow html files to be compressed (see below).

If you set this to anything but '1' it will be ignored, so you can do negative matches.

`SetEnv gzip-only-text/html 1
SetOutputFilter DEFLATE`

Here is an example of enabling compression for the Apache documentation:

`<Directory "/your-server-root/manual">
SetEnv gzip-only-text/html 1
SetOutputFilter DEFLATE
</Directory>`

## DeflateBufferSize Directive

Description: | Fragment size to be compressed at one time by zlib
Syntax: | DeflateBufferSize value
Default: | `DeflateBufferSize 8096`
Context: | server config, virtual host
Status: | Extension
Module: | mod_deflate

The `DeflateBufferSize` directive specifies the size in bytes of the fragments that zlib should compress at one time.

## DeflateFilterNote Directive

Description: | Places the compression ratio in a note for logging
Syntax: | DeflateFilterNote notename
Context: | server config, virtual host
Status: | Extension
Module: | mod_deflate

The `DeflateFilterNote` directive specifies that a note about compression ratios should be attached to the request. The name of the note is the value specified for the directive.

## DeflateMemLevel Directive

Description: | How much memory should be used by zlib for compression
Syntax: | DeflateMemLevel value
Default: | `DeflateMemLevel 9`
Context: | server config, virtual host
Status: | Extension
Module: | mod_deflate

The `DeflateMemLevel` directive specifies how much memory should be used by zlib for compression (a value between 1 and 9).

## DeflateWindowSize Directive

Description: | Zlib compression window size
Syntax: | DeflateWindowSize value
Default: | `DeflateWindowSize 15`
Context: | server config, virtual host
Status: | Extension
Module: | mod_deflate

The `DeflateWindowSize` directive specifies the zlib compression window size (a value between 1 and 15).