A pingback is one of four types of linkback methods for Web authors to request notification when somebody links to one of their documents. This enables authors to keep track of who is linking to, or referring to their articles. Some weblog software and content management systems, such as WordPress, Movable Type, Serendipity, and Telligent Community, support automatic pingbacks where all the links in a published article can be pinged when the article is published. Other content management systems, such as Drupal and Joomla, support pingbacks through the use of addons or extensions.