Instagram is an online mobile photo-sharing, video-sharing, and social networking service that enables its users to take pictures and videos, and share them either publicly or privately on the app, as well as through a variety of other social networking platforms, such as Facebook, Twitter, and Tumblr.

Originally, a distinctive feature of Instagram was that it confined photos to a square shape, in contrast to the 4:3 aspect ratio typically used by mobile device cameras. In 2015 Instagram began allowing users to upload media captured in any aspect ratio.

A popular feature of Instagram is that it enables users to apply digital filters to their images.

Videos on Instagram debuted with a 640×640 fixed resolution and maximum 15-second limit in 2013. Resolutions now include up to 1080p since 2015 and length is now up to 60 seconds as of January 2016.

Instagram was acquired by Facebook in 2012. Since being purchased by Facebook, Instagram has grown by a factor of 3x to 4x of its parent company, largely driven by its popularity among Millennials.