FFT Web is an Out-Of-Tree block which sends a signal FFT by UDP to a websocket server. This websocket server packs and broadcast this FFT data to websockets, which can be opened by html/javascript code for real-time display of the fft in web-browsers (don't worry we are already providing that part ;) ).

FFT Web block come along with the CorteXlab OOT module, but it can also be found on github.