InstaFollowCheck автор hrmtsh

NOTE - Owing to Instagram's inability to show all accounts in the relevant lists, the extension has an accuracy of 90-95%. Do run multiple (2-3 should do) times to confirm results.

"insta_followers_check" is a browser extension (built around firefox, but will work on other chromium browsers with minor tweaks).
it compares your 'followers' and 'following' lists.
it shows -
a. which accounts you follow, but they don't follow you back.
b. which accounts you are followed by, but don't follow back.

usage (for firefox, but similar for chrome etc.) :
1. install extension
2. visit the instagram profile page (https://www.instagram.com/<username>)
3. click on 'followers' or 'following', and reload page.
4. you have 20 sec if on 'followers', and 30 if on 'following', to scroll through the list (to transfer the list of followers/following accounts to the extension).
5. once done with one list, repeat (3) and (4) for other list (one of follower or following).
6. open extension popup from the jigsaw puzzle icon in the top-right of the browser.
7. click buttons and see the relevant lists of accounts on the popup.