XenForo is a commercial Internet forum software package written in the PHP programming language using the Zend Framework. The software is developed by former vBulletin lead developers Kier Darby and Mike Sullivan. The first public beta release of XenForo was released in October 2010. XenForo 1.0.0 Stable was released on March 8, 2011. XenForo has several SEO features built in. Its popularity is growing, according to feedback from various community forums and weblogs.