When trying to implement simple redirects using mod_alias directives in .htaccess, you might find they don't work as expected. Before troubleshooting the rules themselves, it's crucial to verify whether the module is actually loaded in your Apache configuration.

Method 1: Using httpd -M

httpd -M | grep alias
# Expected output if enabled:
#  alias_module (shared)

Method 2: Checking loaded_modules in PHP

<?php
print_r(apache_get_modules());
?>
# Look for 'mod_alias' in the output array

For shared hosting where command line access isn't available:

# Create a test.php file with:
<?php
phpinfo();
?>

Then search for "Loaded Modules" in the output and look for mod_alias.

If you've confirmed mod_alias is enabled but still having issues, try these basic tests:

# Simple redirect test
Redirect 301 /oldpage.html http://example.com/newpage.html

# Alias test
Alias /images /path/to/your/images

• Check Apache error logs for module-related errors
• Ensure AllowOverride includes FileInfo for .htaccess
• Verify the module isn't being overridden by mod_rewrite rules

mod_alias is an Apache module that provides simple URL manipulation through directives like Redirect, RedirectMatch, Alias, and ScriptAlias. Unlike mod_rewrite which offers more complex pattern matching, mod_alias is perfect for straightforward redirect scenarios.

# Example basic mod_alias usage
Redirect 301 /old-page.html https://example.com/new-page.html
RedirectMatch 301 ^/old-dir/(.*)$ https://example.com/new-dir/$1

There are several ways to check if mod_alias is enabled on your Apache server:

Method 1: Using apachectl/httpd Command

# For most Linux systems
apachectl -M | grep alias
# or
httpd -M | grep alias

# Expected output if enabled:
 alias_module (shared)

Method 2: Checking Configuration Files

Inspect your Apache configuration files (typically httpd.conf or apache2.conf) for the LoadModule directive:

grep -r "LoadModule alias_module" /etc/apache2/

Method 3: PHP Info (For Shared Hosting)

If you don't have shell access, create a PHP file with:

<?php phpinfo(); ?>

Then search for "Loaded Modules" in the output.

If you discover mod_alias isn't enabled, here's how to activate it:

# On Debian/Ubuntu
sudo a2enmod alias
sudo systemctl restart apache2

# On CentOS/RHEL
# Edit /etc/httpd/conf/httpd.conf and uncomment:
LoadModule alias_module modules/mod_alias.so
# Then restart Apache
systemctl restart httpd

Even when mod_alias is enabled, directives might not work due to:

• Incorrect file permissions on .htaccess
• AllowOverride not set to FileInfo or All
• Conflicts with mod_rewrite rules
• Syntax errors in the directives

# Redirect single page
Redirect 301 /about.html /about-us.html

# Redirect entire directory
RedirectMatch 301 ^/products/(.*)$ /catalog/$1

# Alias for static files
Alias /downloads "/var/www/special-downloads"
<Directory "/var/www/special-downloads">
    Require all granted
</Directory>

Remember that mod_alias directives execute before mod_rewrite rules, which can affect your expected behavior if both modules are used together.