If you notice your number of Facebook friends decrease by one overnight, you can only wonder which one let you go because Facebook doesn’t make this information available, possibly to prevent bad blood between ‘friends’. But there’s a browser extension/userscript called Unfriend Finder that makes this information readily accessible.
Unfriend Finder for Facebook is a script that allows you to know which one of your friend removes you on Facebook. It also works with people you remove, and people who deactivate their account. The script identifies missing friends by keeping a record of your friend list, and then comparing it to your current friends list on each browser refresh. It’s evident that the script cannot tell you which friends unfriended you in the past, since there is no past record of your friends list to compare. But once the extension is installed, you will be able to discover which of your contacts unfriends you in future.
Unfriend Finder integrates with Facebook’s interface just like an app does and provide real time notifications with an unfriend counter in menubar. You usually start with 0 unfriend; this number may increase over time.
Aside from unfriend notifications, you'll also be able to know which people have not yet accepted or cancelled your friend request. This is another piece of information that Facebook does not reveal.
Unfriend Finder also offers the ability to export and import your preferences, settings and generated Unfriends list to another computer or browser.
Unfriend Finder for Facebook is available for Chrome, Firefox, Opera and Safari.