Launched in 2009 by Dennis Crowley and Naveen Selvadurai, Foursquare is a location-based social networking website for mobile devices. It allows users to “check in” at venues using a mobile website, text messaging or a device-specific application by selecting from a list of venues the application identifies in the nearby region. Location detection is based on GPS hardware in the mobile device or network location provided by the application. Foursquare’s map is based on data from the OpenStreetMap project.