I built this tool around uncovering Facebook advertising interests.
For each keyword you put in the ads manager, Facebook™ shows only 25 interest suggestions, the same that it shows to everybody.
Turns out more interests are just an API call away. If you are a dev, it's pretty simple but I thought to develop a free tool for non-technical people.
This was a small feature of a product I built almost three years ago and decided to give it new life.
It's entirely free to use.
Hope you like it!