apache2 - enable files caching (max-age)

In this short article, we would like to show how to enable cache for website resources (js, css, image, ico and  pdf files) inside apache2 VirtualServer configuration.

The example configuration sets 30 days cache allowing to use publish shared cache (CDNs, etc.).

Quick solution (file /etc/apache2/sites-enabled/my-domain.com.conf):

<VirtualHost *:443>

    ServerName my-domain.com

    # some configurations here ...

    # 30 days cache on public shared caches
    <IfModule mod_headers.c>
        <LocationMatch "\.(ico|pdf|jpe?g|png|gif|js|css)$">
            Header set Cache-Control "max-age=2592000, public"
        </LocationMatch>
    </IfModule>

    # some configurations here ...

</VirtualHost>

Note: run a2enmod headers to enable headers module and restart server with systemctl restart apache2 after configuration is changed.

Where:

• \.(ico|pdf|jpe?g|png|gif|js|css)$ matches files that ends with extensions:
  • ico, pdf,
  • jpg, jpeg, png, gif,
  • js, css,
• max-age sets cache keeping duration (measured in seconds),
  e.g.

  Description	In seconds	Calculation
  60 seconds	60	60s
  60 minutes	3600	60m * 60s
  24 hours	86400	24h * 60m * 60s
  7 days	604800	7d * 24h * 60m * 60s
  30 days	2592000	30d * 24h * 60m * 60s
  12 months	31536000	365d * 24h * 60m * 60s

• public indicates cache keeping strategy,

  HTTP 1.1 allows different values to control cache:

  public	Resources may be cached in public shared caches.
  private	Resources may only be cached in the private cache.
  no-cache	Resources may not be cached.
  no-store	Resources may be cached but not archived.

Note: configuration was tested on Apache 2.4.38 with CloudFlare.

Screenshoot (Google Chrom DevTools):