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16 <p class="apache">Apache HTTP Server Version 2.1</p>
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21 <div id="page-content">
22 <div id="preamble"><h1>Apache Module mod_deflate</h1>
24 <p><span>Available Languages: </span><a href="../en/mod/mod_deflate.html" title="English"> en </a> |
25 <a href="../ja/mod/mod_deflate.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
26 <a href="../ko/mod/mod_deflate.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
28 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Compress content before it is delivered to the
30 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
31 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>deflate_module</td></tr>
32 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_deflate.c</td></tr></table>
35 <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module provides
36 the <code>DEFLATE</code> output filter that allows output from
37 your server to be compressed before being sent to the client over
40 <div id="quickview"><h3 class="directives">Directives</h3>
42 <li><img alt="" src="../images/down.gif" /> <a href="#deflatebuffersize">DeflateBufferSize</a></li>
43 <li><img alt="" src="../images/down.gif" /> <a href="#deflatecompressionlevel">DeflateCompressionLevel</a></li>
44 <li><img alt="" src="../images/down.gif" /> <a href="#deflatefilternote">DeflateFilterNote</a></li>
45 <li><img alt="" src="../images/down.gif" /> <a href="#deflatememlevel">DeflateMemLevel</a></li>
46 <li><img alt="" src="../images/down.gif" /> <a href="#deflatewindowsize">DeflateWindowSize</a></li>
50 <li><img alt="" src="../images/down.gif" /> <a href="#recommended">Sample Configurations</a></li>
51 <li><img alt="" src="../images/down.gif" /> <a href="#enable">Enabling Compression</a></li>
52 <li><img alt="" src="../images/down.gif" /> <a href="#proxies">Dealing with proxy servers</a></li>
53 </ul><h3>See also</h3>
55 <li><a href="../filter.html">Filters</a></li>
57 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
59 <h2><a name="recommended" id="recommended">Sample Configurations</a></h2>
60 <p>This is a simple sample configuration for the impatient.</p>
62 <div class="example"><h3>Compress only a few types</h3><p><code>
63 AddOutputFilterByType DEFLATE text/html text/plain text/xml
66 <p>The following configuration, while resulting in more compressed content,
67 is also much more complicated. Do not use this unless you fully understand
68 all the configuration details.</p>
70 <div class="example"><h3>Compress everything except images</h3><p><code>
71 <Location /><br />
74 SetOutputFilter DEFLATE<br />
76 # Netscape 4.x has some problems...<br />
77 BrowserMatch ^Mozilla/4 gzip-only-text/html<br />
79 # Netscape 4.06-4.08 have some more problems<br />
80 BrowserMatch ^Mozilla/4\.0[678] no-gzip<br />
82 # MSIE masquerades as Netscape, but it is fine<br />
83 # BrowserMatch \bMSIE !no-gzip !gzip-only-text/html<br />
85 # NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48<br />
86 # the above regex won't work. You can use the following<br />
87 # workaround to get the desired effect:<br />
88 BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html<br />
90 # Don't compress images<br />
91 SetEnvIfNoCase Request_URI \<br />
93 \.(?:gif|jpe?g|png)$ no-gzip dont-vary<br />
96 # Make sure proxies don't deliver the wrong content<br />
97 Header append Vary User-Agent env=!dont-vary<br />
102 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
103 <div class="section">
104 <h2><a name="enable" id="enable">Enabling Compression</a></h2>
106 <h3><a name="output" id="output">Output Compression</a></h3>
107 <p>Compression is implemented by the <code>DEFLATE</code>
108 <a href="../filter.html">filter</a>. The following directive
109 will enable compression for documents in the container where it
112 <div class="example"><p><code>
113 SetOutputFilter DEFLATE
116 <p>Some popular browsers cannot handle compression of all content
117 so you may want to set the <code>gzip-only-text/html</code> note to
118 <code>1</code> to only allow html files to be compressed (see
119 below). If you set this to <em>anything but <code>1</code></em> it
122 <p>If you want to restrict the compression to particular MIME types
123 in general, you may use the <code class="directive"><a href="../mod/core.html#addoutputfilterbytype">AddOutputFilterByType</a></code> directive. Here is an example of
124 enabling compression only for the html files of the Apache
127 <div class="example"><p><code>
128 <Directory "/your-server-root/manual"><br />
129 <span class="indent">
130 AddOutputFilterByType DEFLATE text/html<br />
135 <p>For browsers that have problems even with compression of all file
136 types, use the <code class="directive"><a href="../mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code> directive to set the <code>no-gzip</code>
137 note for that particular browser so that no compression will be
138 performed. You may combine <code>no-gzip</code> with <code>gzip-only-text/html</code> to get the best results. In that case
139 the former overrides the latter. Take a look at the following
140 excerpt from the <a href="#recommended">configuration example</a>
141 defined in the section above:</p>
143 <div class="example"><p><code>
144 BrowserMatch ^Mozilla/4 gzip-only-text/html<br />
145 BrowserMatch ^Mozilla/4\.0[678] no-gzip<br />
146 BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
149 <p>At first we probe for a <code>User-Agent</code> string that
150 indicates a Netscape Navigator version of 4.x. These versions
151 cannot handle compression of types other than
152 <code>text/html</code>. The versions 4.06, 4.07 and 4.08 also
153 have problems with decompressing html files. Thus, we completely
154 turn off the deflate filter for them.</p>
156 <p>The third <code class="directive"><a href="../mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code>
157 directive fixes the guessed identity of the user agent, because
158 the Microsoft Internet Explorer identifies itself also as "Mozilla/4"
159 but is actually able to handle requested compression. Therefore we
160 match against the additional string "MSIE" (<code>\b</code> means
161 "word boundary") in the <code>User-Agent</code> Header and turn off
162 the restrictions defined before.</p>
164 <div class="note"><h3>Note</h3>
165 The <code>DEFLATE</code> filter is always inserted after RESOURCE
166 filters like PHP or SSI. It never touches internal subrequests.
168 <div class="note"><h3>Note</h3>
169 There is a environment variable <code>force-gzip</code>,
170 set via <code class="directive"><a href="../mod/core.html#setenv">SetEnv</a></code>, which
171 will ignore the accept-encoding setting of your browser and will
172 send compressed output.
176 <h3><a name="inflate" id="inflate">Output Decompression</a></h3>
177 <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module also provides a filter for
178 inflating/uncompressing a gzip compressed response body. In order to activate
179 this feature you have to insert the <code>INFLATE</code> filter into
180 the outputfilter chain using <code class="directive"><a href="../mod/core.html#setoutputfilter">SetOutputFilter</a></code> or <code class="directive"><a href="../mod/mod_mime.html#addoutputfilter">AddOutputFilter</a></code>, for example:</p>
182 <div class="example"><p><code>
183 <Location /dav-area><br />
184 <span class="indent">
185 ProxyPass http://example.com/<br />
186 SetOutputFilter INFLATE<br />
191 <p>This Example will uncompress gzip'ed output from example.com, so other
192 filters can do further processing with it.
196 <h3><a name="input" id="input">Input Decompression</a></h3>
197 <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module also provides a filter for
198 decompressing a gzip compressed request body . In order to activate
199 this feature you have to insert the <code>DEFLATE</code> filter into
200 the input filter chain using <code class="directive"><a href="../mod/core.html#setinputfilter">SetInputFilter</a></code> or <code class="directive"><a href="../mod/mod_mime.html#addinputfilter">AddInputFilter</a></code>, for example:</p>
202 <div class="example"><p><code>
203 <Location /dav-area><br />
204 <span class="indent">
205 SetInputFilter DEFLATE<br />
210 <p>Now if a request contains a <code>Content-Encoding:
211 gzip</code> header, the body will be automatically decompressed.
212 Few browsers have the ability to gzip request bodies. However,
213 some special applications actually do support request
214 compression, for instance some <a href="http://www.webdav.org">WebDAV</a> clients.</p>
216 <div class="warning"><h3>Note on Content-Length</h3>
217 <p>If you evaluate the request body yourself, <em>don't trust
218 the <code>Content-Length</code> header!</em>
219 The Content-Length header reflects the length of the
220 incoming data from the client and <em>not</em> the byte count of
221 the decompressed data stream.</p>
224 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
225 <div class="section">
226 <h2><a name="proxies" id="proxies">Dealing with proxy servers</a></h2>
228 <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module sends a <code>Vary:
229 Accept-Encoding</code> HTTP response header to alert proxies that
230 a cached response should be sent only to clients that send the
231 appropriate <code>Accept-Encoding</code> request header. This
232 prevents compressed content from being sent to a client that will
233 not understand it.</p>
235 <p>If you use some special exclusions dependent
236 on, for example, the <code>User-Agent</code> header, you must
237 manually configure an addition to the <code>Vary</code> header
238 to alert proxies of the additional restrictions. For example,
239 in a typical configuration where the addition of the <code>DEFLATE</code>
240 filter depends on the <code>User-Agent</code>, you should add:</p>
242 <div class="example"><p><code>
243 Header append Vary User-Agent
246 <p>If your decision about compression depends on other information
247 than request headers (<em>e.g.</em> HTTP version), you have to set the
248 <code>Vary</code> header to the value <code>*</code>. This prevents
249 compliant proxies from caching entirely.</p>
251 <div class="example"><h3>Example</h3><p><code>
255 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
256 <div class="directive-section"><h2><a name="DeflateBufferSize" id="DeflateBufferSize">DeflateBufferSize</a> <a name="deflatebuffersize" id="deflatebuffersize">Directive</a></h2>
257 <table class="directive">
258 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Fragment size to be compressed at one time by zlib</td></tr>
259 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateBufferSize <var>value</var></code></td></tr>
260 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateBufferSize 8096</code></td></tr>
261 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
262 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
263 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr>
265 <p>The <code class="directive">DeflateBufferSize</code> directive specifies
266 the size in bytes of the fragments that zlib should compress at one
270 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
271 <div class="directive-section"><h2><a name="DeflateCompressionLevel" id="DeflateCompressionLevel">DeflateCompressionLevel</a> <a name="deflatecompressionlevel" id="deflatecompressionlevel">Directive</a></h2>
272 <table class="directive">
273 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>How much compression do we apply to the output</td></tr>
274 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateCompressionLevel <var>value</var></code></td></tr>
275 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Zlib's default</code></td></tr>
276 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
277 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
278 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr>
279 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>This directive is available since Apache 2.0.45</td></tr>
281 <p>The <code class="directive">DeflateCompressionLevel</code> directive specifies
282 what level of compression should be used, the higher the value,
283 the better the compression, but the more CPU time is required to
285 <p>The value must between 1 (less compression) and 9 (more compression).</p>
288 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
289 <div class="directive-section"><h2><a name="DeflateFilterNote" id="DeflateFilterNote">DeflateFilterNote</a> <a name="deflatefilternote" id="deflatefilternote">Directive</a></h2>
290 <table class="directive">
291 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Places the compression ratio in a note for logging</td></tr>
292 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateFilterNote [<var>type</var>] <var>notename</var></code></td></tr>
293 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
294 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
295 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr>
296 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td><var>type</var> is available since Apache 2.0.45</td></tr>
298 <p>The <code class="directive">DeflateFilterNote</code> directive
299 specifies that a note about compression ratios should be attached
300 to the request. The name of the note is the value specified for
301 the directive. You can use that note for statistical purposes by
302 adding the value to your <a href="../logs.html#accesslog">access log</a>.</p>
304 <div class="example"><h3>Example</h3><p><code>
305 DeflateFilterNote ratio<br />
307 LogFormat '"%r" %b (%{ratio}n) "%{User-agent}i"' deflate<br />
308 CustomLog logs/deflate_log deflate
311 <p>If you want to extract more accurate values from your logs, you
312 can use the <var>type</var> argument to specify the type of data
313 left as note for logging. <var>type</var> can be one of:</p>
316 <dt><code>Input</code></dt>
317 <dd>Store the byte count of the filter's input stream in the note.</dd>
319 <dt><code>Output</code></dt>
320 <dd>Store the byte count of the filter's output stream in the note.</dd>
322 <dt><code>Ratio</code></dt>
323 <dd>Store the compression ratio (<code>output/input * 100</code>)
324 in the note. This is the default, if the <var>type</var> argument
328 <p>Thus you may log it this way:</p>
330 <div class="example"><h3>Accurate Logging</h3><p><code>
331 DeflateFilterNote Input instream<br />
332 DeflateFilterNote Output outstream<br />
333 DeflateFilterNote Ratio ratio<br />
335 LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate<br />
336 CustomLog logs/deflate_log deflate
341 <li><code class="module"><a href="../mod/mod_log_config.html">mod_log_config</a></code></li>
344 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
345 <div class="directive-section"><h2><a name="DeflateMemLevel" id="DeflateMemLevel">DeflateMemLevel</a> <a name="deflatememlevel" id="deflatememlevel">Directive</a></h2>
346 <table class="directive">
347 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>How much memory should be used by zlib for compression</td></tr>
348 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateMemLevel <var>value</var></code></td></tr>
349 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateMemLevel 9</code></td></tr>
350 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
351 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
352 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr>
354 <p>The <code class="directive">DeflateMemLevel</code> directive specifies
355 how much memory should be used by zlib for compression
356 (a value between 1 and 9).</p>
359 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
360 <div class="directive-section"><h2><a name="DeflateWindowSize" id="DeflateWindowSize">DeflateWindowSize</a> <a name="deflatewindowsize" id="deflatewindowsize">Directive</a></h2>
361 <table class="directive">
362 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Zlib compression window size</td></tr>
363 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateWindowSize <var>value</var></code></td></tr>
364 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateWindowSize 15</code></td></tr>
365 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
366 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
367 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr>
369 <p>The <code class="directive">DeflateWindowSize</code> directive specifies the
370 zlib compression window size (a value between 1 and 15). Generally, the
371 higher the window size, the higher can the compression ratio be expected.</p>
375 <div class="bottomlang">
376 <p><span>Available Languages: </span><a href="../en/mod/mod_deflate.html" title="English"> en </a> |
377 <a href="../ja/mod/mod_deflate.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
378 <a href="../ko/mod/mod_deflate.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
379 </div><div id="footer">
380 <p class="apache">Copyright 1999-2004 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
381 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>