Instagram is an online service where people can share their photos adding filters and effects for more attention, creative people get followers and fame but these followers might unfollow you for some or other reason so its important to see who unfollows you and why, well for this stuff Unfollowgram online service comes in than simply tracks every follower on your account and if you unfollows you you get notified.
So now Unfollowgram does two things quit easily, one to track who unfollowed you on Instagram and the second one is checking who do not follow you back. So if you are following someone and he does not follow you back than it tracks that thing too.
The best part is that it works on mobile devices too with desktop awesomeness. So now you can visit their website and login with your Instagram account, you obviously need to grant access to their service.
So now have fun checking out who exactly unfollows you on Instagram.