CodeIgniter is one of the world’s most popular Open Source PHP frameworks, used by thousands of developers powering hundreds of thousands of sites, in addition to being deployed as the underpinning of every ExpressionEngine installation. As of this writing it is the second most watched PHP project hosted at GitHub, surpassing Slim, Yii, CakePHP, Zend, and Laravel in either followers, contributors, or both. It has the highest number of forks of any PHP project at GitHub of all time. It is used by everyone from AT&T to Home Depot to Dictionary.com, to Rachael Ray to Magento to the Mail & Guardian, to the Universities of Missouri, Michigan, Texas, Georgia, and more (Sources: builtwith.com, wappalyzer.com). And it is used as the server-side back end for many mobile apps.