According to BuiltWith , of the top million websites using content management systems (or CMSes), three systems own more than 75 percent of the total market share: WordPress , Joomla , and Drupal . (All of which are open source, by the way.) Many are likely most familiar with WordPress, which TechCrunch has covered quite a bit (and uses to power most its sites, for full disclosure). WordPress is the most popular CMS on the Web, running 62 percent of the top million websites that use a CMS, according to BuiltWith, with Joomla now ranking second at 10 percent and closing.