The easiest way to track Instagram unfollows is a web tool that only needs a username. No app download, no Instagram password, and no account to see your first result. You open the page, type a public @username, and run a scan.
That is the whole pitch, and the step count is the proof. Three actions get you from curious to a real answer: open the site, enter a username, read the results. Most trackers make you install an app and sign in before they show you anything. This one skips both.
One honest caveat belongs up front, and the rest of this guide comes back to it: the first scan sets your baseline. Unfollows show up on the next scan, once there is an earlier list to compare against. Easy does not mean instant time travel.