How to Enable Gzip or Deflate Compression in .htaccess: Best Practices & Code Examples


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Both Gzip and Deflate are popular compression methods for reducing file sizes before sending them to clients. Gzip is more widely supported and often preferred due to better compression ratios, while Deflate is faster but less efficient. Modern servers typically use Gzip by default.

Here's how to enable compression in your .htaccess file:


<IfModule mod_deflate.c>
  # Compress HTML, CSS, JavaScript, Text, XML and fonts
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
  AddOutputFilterByType DEFLATE application/x-font
  AddOutputFilterByType DEFLATE application/x-font-opentype
  AddOutputFilterByType DEFLATE application/x-font-otf
  AddOutputFilterByType DEFLATE application/x-font-truetype
  AddOutputFilterByType DEFLATE application/x-font-ttf
  AddOutputFilterByType DEFLATE application/x-javascript
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE font/opentype
  AddOutputFilterByType DEFLATE font/otf
  AddOutputFilterByType DEFLATE font/ttf
  AddOutputFilterByType DEFLATE image/svg+xml
  AddOutputFilterByType DEFLATE image/x-icon
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/javascript
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/xml
  
  # Remove browser bugs (only needed for ancient browsers)
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4\.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
  Header append Vary User-Agent
</IfModule>

For better control over compression levels:


<IfModule mod_deflate.c>
  # Set compression level (1-9)
  DeflateCompressionLevel 6
  
  # Force compression for mangled headers
  <IfModule mod_setenvif.c>
    <IfModule mod_headers.c>
      SetEnvIfNoCase ^(Accept-EncodXng|X-cept-Encoding|X{15}|~{15}|-{15})$ ^((gzip|deflate)\s*,?\s*)+|[X~-]{4,13}$ HAVE_Accept-Encoding
      RequestHeader append Accept-Encoding "gzip,deflate" env=HAVE_Accept-Encoding
    </IfModule>
  </IfModule>
</IfModule>

If you prefer using mod_gzip (requires separate module):


<IfModule mod_gzip.c>
  mod_gzip_on Yes
  mod_gzip_dechunk Yes
  mod_gzip_item_include file \.(html?|txt|css|js|php|pl)$
  mod_gzip_item_include handler ^cgi-script$
  mod_gzip_item_include mime ^text/.*
  mod_gzip_item_include mime ^application/x-javascript.*
  mod_gzip_item_exclude mime ^image/.*
  mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</IfModule>

After implementing these changes, verify compression is working using:


curl -I -H "Accept-Encoding: gzip,deflate" http://yourdomain.com

Look for "Content-Encoding: gzip" in the response headers.

While compression improves load times, consider these factors:

  • Compression level 6 offers the best balance between CPU usage and compression ratio
  • Don't compress already compressed files (JPEG, PNG, GIF)
  • Modern browsers support Brotli compression (requires server support)

When it comes to web performance optimization, Gzip and Deflate are two of the most widely used compression methods. Both work by compressing text-based files (HTML, CSS, JavaScript) before sending them to the client, significantly reducing file sizes and improving load times.

While both methods are effective, Gzip has become the de facto standard in recent years. Most modern browsers support Gzip compression (with the "Accept-Encoding: gzip" header), and it typically offers slightly better compression ratios than Deflate.

Here's a comprehensive .htaccess configuration that enables Gzip compression for all compatible file types:

# Enable Gzip Compression
<IfModule mod_deflate.c>
  # Compress HTML, CSS, JavaScript, Text, XML and fonts
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
  AddOutputFilterByType DEFLATE application/x-font
  AddOutputFilterByType DEFLATE application/x-font-opentype
  AddOutputFilterByType DEFLATE application/x-font-otf
  AddOutputFilterByType DEFLATE application/x-font-truetype
  AddOutputFilterByType DEFLATE application/x-font-ttf
  AddOutputFilterByType DEFLATE application/x-javascript
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE font/opentype
  AddOutputFilterByType DEFLATE font/otf
  AddOutputFilterByType DEFLATE font/ttf
  AddOutputFilterByType DEFLATE image/svg+xml
  AddOutputFilterByType DEFLATE image/x-icon
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/javascript
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/xml

  # Remove browser bugs (only needed for old browsers)
  BrowserMatch ^Mozilla/4 gzip-only-text/html
  BrowserMatch ^Mozilla/4\.0[678] no-gzip
  BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
  Header append Vary User-Agent
</IfModule>

If you prefer to use Deflate compression instead, here's the equivalent setup:

# Enable Deflate Compression
<IfModule mod_deflate.c>
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/xml
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/x-javascript
</IfModule>

After implementing these changes, verify compression is working using:

  • Browser Developer Tools (check Response Headers for "Content-Encoding: gzip")
  • Online tools like GIDNetwork's Compression Test or Google's PageSpeed Insights
  • Command line: curl -I -H "Accept-Encoding: gzip,deflate" http://yourdomain.com

While compression improves transfer times, be aware of these factors:

  • CPU overhead: Compression requires server resources
  • Already compressed files (images, PDFs) shouldn't be compressed again
  • Cache settings should be properly configured alongside compression

For fine-tuned control, you can adjust compression level (1-9) and other parameters:

# Advanced Gzip Configuration
<IfModule mod_deflate.c>
  # Compression level (1-9)
  DeflateCompressionLevel 6
  
  # Skip compression for very small files
  DeflateFilterNote Input instream
  DeflateFilterNote Output outstream
  DeflateFilterNote Ratio ratio
  LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate
  CustomLog logs/deflate_log deflate
</IfModule>