Optimized `mod_expires` Settings for Apache

The mod_expires module in Apache is used for controlling the setting of the Expires HTTP header and the max-age directive of the Cache-Control HTTP header in server responses. These headers determine how long a client (browser or proxy) will cache resources. Optimizing these settings can significantly reduce server load and improve client-side experience by reducing load times.

Optimized mod_expires Settings

Here’s an optimized mod_expires section for a production server, covering a variety of file types:

## EXPIRES CACHING ##
<IfModule mod_expires.c>
    ExpiresActive On

    # Default expiration: 1 hour after request
    ExpiresDefault "now plus 1 hour"

    # HTML components
    ExpiresByType text/html "access plus 0 seconds"

    # Data interchange
    ExpiresByType application/json "access plus 0 seconds"
    ExpiresByType application/xml "access plus 0 seconds"
    ExpiresByType application/rss+xml "access plus 1 hour"
    ExpiresByType application/atom+xml "access plus 1 hour"

    # Favicon (can be cached for a long time)
    ExpiresByType image/x-icon "access plus 1 year"

    # Media: images, video, audio
    ExpiresByType image/gif "access plus 1 month"
    ExpiresByType image/png "access plus 1 month"
    ExpiresByType image/jpeg "access plus 1 month"
    ExpiresByType image/webp "access plus 1 month"
    ExpiresByType video/ogg "access plus 1 month"
    ExpiresByType audio/ogg "access plus 1 month"
    ExpiresByType video/mp4 "access plus 1 month"
    ExpiresByType video/webm "access plus 1 month"

    # CSS and JavaScript
    ExpiresByType text/css "access plus 1 year"
    ExpiresByType application/javascript "access plus 1 year"
    ExpiresByType application/x-javascript "access plus 1 year"
    ExpiresByType text/javascript "access plus 1 year"

    # Webfonts
    ExpiresByType font/otf "access plus 1 month"
    ExpiresByType font/ttf "access plus 1 month"
    ExpiresByType font/woff "access plus 1 month"
    ExpiresByType font/woff2 "access plus 1 month"
    ExpiresByType application/font-woff "access plus 1 month"
    ExpiresByType application/font-woff2 "access plus 1 month"
    ExpiresByType image/svg+xml "access plus 1 month"

    # Other
    ExpiresByType application/pdf "access plus 1 month"
    ExpiresByType image/vnd.microsoft.icon "access plus 1 year"
</IfModule>

Explanation of Settings

• ExpiresDefault: This is the default caching time for resources that don’t match other rules. It’s set to 1 hour, but you can adjust it based on how often your content changes.
• HTML and Data Interchange: These types of content usually change frequently and are set to expire immediately (0 seconds) or after a short period (1 hour for feeds).
• Favicons: These rarely change and can be cached for a longer period (1 year).
• Media Files: Images, videos, and audios are typically not updated frequently. They are set to expire in 1 month, but this can be increased if these resources rarely change.
• CSS and JavaScript: As these files might change with website updates, but not as frequently as HTML content, they are set to a longer cache period (1 year). Ensure versioning of these files to avoid caching issues when they are updated.
• Webfonts: Fonts generally don’t change once they are set, so a longer caching period (1 month) is appropriate.
• Other Types: For resources like PDFs and specific image types, adjust the caching time based on how often these resources are updated.

Additional Notes

• Adjust these settings based on your specific content update frequency.
• Ensure you have a versioning strategy for assets like CSS and JavaScript to prevent caching issues when these files are updated.
• Keep in mind that aggressive caching might lead to issues when content is updated on the server but still cached in the client’s browser.
• Regularly monitor and adjust these settings based on the specific needs and feedback from the production environment.