Caravel is described as 'Free project management tool for UX and agile teams. It allows teams to share design guidelines and deliverables with clients and stakeholders (from personas to final UX/UI screens)' and is a UI Design tool. There are more than 10 alternatives to Caravel for a variety of platforms, including Web-based, Android, iPhone, Android Tablet and iPad apps. The best Caravel alternative is Balsamiq Wireframes. It's not free, so if you're looking for a free alternative, you could try Wireflow or Moqups. Other great apps like Caravel are InVision, Marvel, mydraft.cc and Studio.Design.