See which tracks in a playlist you have already heard, and keep only the new ones. Your Last.fm history, applied to your Spotify playlists.
Connect your Spotify account and your Last.fm profile. The app reads your playlists from Spotify and your listening history from Last.fm, and puts them side by side.
Nothing is kept on the server: your settings, your session and cached answers stay in this browser.
Setup takes about five minutes: you create your own Spotify app and a Last.fm API key, and the guide walks you through both.