Joomla! Documentation™

• Disallow non-SEF URLs: Enabling this option means that Joomla will try to build the correct URL from what it understood of the current URL and if the current URL and the one Joomla built itself are not identical, Joomla will redirect to the one it built itself. This means that URLs like /component/content/article/42 or index.php?option=com_content&view=article&id=42 would be correctly redirected to /welcome/to/joomla. This option can create issues in some site setups, so test your site thoroughly after enabling this.