How do you know who follows and unfollows you on Twitter?

There is a notification that who followed you but there is no way to who unfollowed you if you have a huge list of followers.

Tracking followers is easy on Twitter, but tracking unfollowers isn’t. Because Twitter doesn’t provide any data for tracking unfollowers. That’s why I use the tool FollowersAudit. FollowerAudit is a Twitter followers and unfollowers tracking tool, which can provide you these stats for your as well as any other public Twitter account. You will get a list of all the followers and unfollowers.

Twitter doesn't provide this data thus we need to use thirdparty tools like unfollowerstats.com