Link shorteners: the long and short of why you shouldn’t use them
I worked with an org that ran their own link shortener... and used it for confirmation links! I'm not even kidding, you'd go to reset you password and as expected the link would be something like:    ourapp.example.com/auth/reset?user=blah&token=1af17e73721dbe0c40011b82ed4bb1a7dbe3ce29eae4997c84600287f8866673d05fdaa1aa841a5a

and they they figured, oh man, those links are unsightly for email, we'd best turn that into something like:    ourapp.example.com/s/xO8pR

That looks way cleaner in an email.