There are several apps you can download and use for know who unfollowed you on Instagram.
Figuring out who like your posts or comment under your Instagram posts is easy instagram also with insights allow business account to analyize users. But in case you want to know who unfollowed you, is a little tricky. Of course, the manual method is not efficient, some users go to follower scroll down to see which account is missing. It is not a smart way, who can take it, it takes time like forever.
We call these kinds of the app third party applications, which means, Instagram does not provide these apps but these apps can work with Instagram.
1) Follower Meter for Instagram
With this app, you can see who followed you back or who you don not followed her/him back? Who has unfollowed you your new? Who are new followers?
2) Followers tracker pro
This app is very similar to the first app that I have mentioned but with a new format and user interface. There is a list with numbers that show who blocked you, who follow you back, who is following, and who unfollowed you on Instagram and, so on. There is a problem with this app. If you install this app today, you can see who blocked you today not last week. If you need that information this application cannot provide it.
This app also has features like who your ghost followers are, who my top likers are. But like many useful features, this feature comes with a cost. You have to go premium to see this information. My recommendation is to use the premium for deeper analytic data.
Who is the ghost follower?
Users that never do something, never like, comment, or engage, they are bots.
Some business accounts try to follow you and after you follow back, they unfollow you. They play follow- unfollow to get more followers on Instagram. Now you know who unfollowed you, you also unfollow them and try not to win them back