Using Drupal, you can configure several smaller websites to share a common set of Drupal core files, contributed modules, and theme files. All these websites share a common docroot directory. This is called multisite Drupal.

Acquia uses Drupal’s multisite feature with its Site Factory products to provide a Drupal software as a service experience, allowing many users access to their own Drupal website development environments.

Using multisite naming tools (such as the sites.php file) and naming conventions (such as naming a multisite directory your website’s URL), requests for specific URLs can be routed to specific Drupal multisite directories. By default, these directories are located at docroot/sites/multisite-directory.

When working with a single application, Drupal core updates or module updates in the /sites/all/modules folder will affect all the multisites in the docroot directory. This behavior can be useful when rolling out updates and security fixes, but can also require caution, as changes that work fine with one multisite website may not work as intended on other websites in the multisite application. As with any Drupal implementation, be sure to test any changes across several multisite websites and to follow standard security procedures.

For information about setting up multisites on Cloud Platform, see About Drupal multisite installations.