Q. What is the difference between posting a video to Instagram and to IGTV?

A. Instagram, originally an app for posting square smartphone photos, added support for 15-second video clips in 2013. The platform now allows videos up to 60 seconds, and the clips can be in the horizontal format.

This summer, Instagram announced its new stand-alone IGTV app for sharing longer video. (People using the main Instagram app can also watch IGTV videos by tapping the TV icon in the top-right corner of the screen.) However, IGTV has its own specific requirements for videos.