Instagram is an online mobile photo sharing site that allows you to take pictures and share them publicly or privately on the app as well as through a variety of other social networking sites such as Facebook, Twitter, Tumblr, and Flickr. Originally a distinctive feature was that it confined photos to a square shape similar to Kodak Instamatic and Polaroid SX-70 images in contrast to the 4:3 aspect ratio typically used by mobile device cameras.allowing users to upload media captured in any aspect ratio. Users can also apply digital filters to their images. Videos on Instagram definition resolution clips of up to 15 seconds to be shared later improvements added support for widescreen resolutions of up to 1080p and longer recording times up to one minute videos.Instagram a free mobile app. The service rapidly gained popularity with over 100 million active users and over 300 million. the app is available for iPhone, iPad, iPod Touch,Windows 10 devices and Android handsets, while third-party Instagram apps are available for BlackBerry 10 and Nokia-Symbian Devices.