Remove Drupal stylesheets with hook_css_alter

When you start building Drupal themes, you quickly find a lot of default stylesheets in the page. If you want to remove some of them from your theme, implement hook_css_alter in template.php and unset the files you do not want.

Here is a small example:

<?php
/**
 * Remove Drupal's core system stylesheets.
 */
function THEMENAME_css_alter(&$css)
{
    $path_system = drupal_get_path('module', 'system');

    $remove = array(
        $path_system . '/system.base.css',
        $path_system . '/system.menus.css',
        $path_system . '/system.messages.css',
        $path_system . '/system.theme.css',
    );

    // Remove stylesheets which match our remove array.
    foreach ($css as $stylesheet => $options) {
        if (in_array($stylesheet, $remove)) {
            unset($css[$stylesheet]);
        }
    }
}

This removes the system module stylesheets before Drupal renders them. The same pattern works for any module stylesheet you want to remove.