Spotify Discover Weekly: how it picks songs you've never heard

Nobody at Spotify picks your Discover Weekly. A system builds it for you, and it does that by combining three different signals about music.

One caveat first. Spotify has not published its exact system, so what follows is a simplified view based on public descriptions. Treat it as a mental model, not a spec.

Signal one, people who listen like you

The first signal is other listeners. The system looks at the people who play the same songs you do. If those people love a song you haven't played, that song becomes a candidate for your playlist.

Notice what's missing here. Nothing in this step is about the song itself. It only needs overlap between your listening and theirs. If your taste lines up with a group, their favorites you haven't heard are the obvious place to look.

Signal two, what the internet writes

The second signal is text. The system reads what the internet writes about songs, and songs described in similar words get grouped together.

So the grouping comes from language. If people describe two songs in similar words, those songs end up near each other, and a song near ones you already like is a reasonable thing to suggest.

Signal three, the audio itself

The third signal is the sound. The system listens to the audio itself and finds songs that sound alike.

This works even if nobody has played a song yet. Listener overlap needs someone to have played it. The audio is already there, so it can be matched to songs that sound similar.

Why it's mixed

It's not one trick. The playlist draws on your taste, other people's taste and the sound itself, mixed together.

That also explains the odd feeling of the playlist. A song you've never heard can land for any of those reasons, and from the outside you can't tell which one it was.

What to do with this

If you build recommendations of any kind, the useful idea is to avoid betting on one signal. Look at behavior, text and content together.

If you're a listener, try this. The next time a Discover Weekly track lands, ask which of the three signals might have put it there. And if you know someone who says that playlist is all luck, send them this page.