Instagram is a free photo and video sharing app available on iPhone and Android. People can upload photos or videos to our service and share them with their followers or with a select group of friends. They can also view, comment and like posts shared by their friends on Instagram.

Instagram was started in San Francisco by Kevin Systrom and Mike Krieger, who initially tried creating a platform similar to Foursquare but then turned their attention exclusively to photo sharing. The word Instagram is an amalgam of "instant camera" and "telegram."

1. Instagram (669m followers) Finally, Instagram's official account is way out in front, with over 669m followers. The feed has a clear purpose – to show off the best and the most interesting people and trends on Instagram.