Enable mod_headers and Verify That mod_expires is Working in Apache

This guide walks through both Apache modules together: enable mod_headers (which sets HTTP response headers) and verify mod_expires (which controls browser caching). For the per-module deep dives, see How to Install and Enable mod_headers in Apache, How to Enable and Configure mod_headers in Apache, Understanding mod_headers in Apache, How to Enable and Configure mod_expires in Apache for Caching, and the parallel Vary: Accept-Encoding Header in Apache.

apachectl -M | grep headers

Expected output:

headers_module (shared)

If mod_headers is not enabled, proceed with enabling it.

Enable mod_headers

For Debian/Ubuntu

sudo a2enmod headers
sudo systemctl restart apache2

For CentOS/RHEL

Ensure mod_headers is loaded in Apache's configuration file:

sudo nano /etc/httpd/conf/httpd.conf

Find or add:

LoadModule headers_module modules/mod_headers.so

Restart Apache:

sudo systemctl restart httpd

Test if mod_headers is working by running:

curl -I http://yourdomain.com

Expected output (example):

X-Frame-Options: DENY
X-Content-Type-Options: nosniff

Verify That mod_expires is Working

Check if mod_expires is Enabled

Run:

apachectl -M | grep expires

Expected output:

expires_module (shared)

If mod_expires is not enabled, enable it.

For Debian/Ubuntu

sudo a2enmod expires
sudo systemctl restart apache2

For CentOS/RHEL

Ensure mod_expires is loaded in Apache's configuration file:

sudo nano /etc/httpd/conf/httpd.conf

Find or add:

LoadModule expires_module modules/mod_expires.so

Restart Apache:

sudo systemctl restart httpd

Check HTTP Headers for mod_expires

Run:

curl -I http://yourdomain.com/path-to-image.jpg

Expected output:

Cache-Control: max-age=15552000
Expires: Tue, 10 Sep 2024 12:00:00 GMT

If the headers are missing, check Apache logs:

sudo tail -f /var/log/apache2/error.log

or for CentOS:

sudo tail -f /var/log/httpd/error_log

Summary of Fixes

Now both mod_headers and mod_expires are enabled and verified!