Who doesn't follow me back on Instagram?
Instagram doesn't provide one simple list showing every account you follow that doesn't follow you back. FollowerSpotter automates that comparison in Chrome.
How the comparison works
FollowerSpotter reads your Followers list and your Following list during a user-started scan, then calculates the difference: accounts in Following that are not present in Followers.
Why use a browser extension?
The extension works from the Instagram session already open in your browser, so there is no separate username list to copy and paste into a website.