The functionality of Live Photos on iPhones has become quite handy, as it is possible to choose the perfect shot (key photo) for each photo. The new Live Photo feature is turned on by default on iPhone 6S and later according to https://support.apple.com/en-us/HT207310
Choosing the right key photo is based on an additional video stream which is stored along with the “normal” (key) photo. Out of this reason, the allocated space for each photo almost doubles up. If you download your photos and videos from your iPhone, you’ll recognize that you can certainly get rid of unnecessary videos, which are just kept for Live Photo reasons.
NOTE: Once you delete those video files, you won’t be able to change their key photos anymore.
So how do you know the differences between a Live Photo video, a slo-mo video and a normal video? Live Photo videos usually take between 1 and 3 seconds, but maybe you recorded a real video by purpose, having the same duration…
Even though the frame rate of different video types varies mostly, there is a static and unique attribute which maps to the video type. This attribute is part of the EXIF information of each photo and is called “Frame width”.
Here’s a screenshot of various EXIF attributes for different video types (based on an iPhone 7):
