Loopt was a company based in Mountain View, California, United States which provided a service for smartphone users to share their location selectively with other people (see location-based service). The service supported iPhone, BlackBerry, Android and Windows Phones. Loopt's services had more than five million registered users and partnerships with every major U.S. mobile phone carrier. Their applications offered a variety of privacy controls. In addition to its core features, users also had the ability to integrate Loopt with other social networks, including Facebook and Twitter.