If you’ve ever used the shuffle button on Spotify, you’ve probably noticed that it often doesn’t feel random at all. As it turns out, this is by design, and there are actually a lot of things that go into how shuffle works on Spotify.
You are not alone if this is a complaint you have had. The Spotify and Reddit support forums are full of people voicing their complaints about the shuffle feature. It clearly doesn’t work the way people expect it to. Let’s take a look at why that is.
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Random doesn’t feel random
The core of this situation is ours. perception of what is random versus how random works in the real world. The common complaint is that Spotify’s shuffle doesn’t feel random, but true shuffle isn’t what we really want.
Flipping a quarter is a good example of this. If the coin is tossed 10 times, we expect to see a relatively even distribution of heads and tails. However, true chance can easily result in 10 consecutive heads. Every time the coin is tossed, there is a 50/50 chance that it will come up heads or tails. That chance does not change depending on the previous coin toss.
The same applies to the songs in a playlist. True chance could end up playing the same artist multiple times in a row – there’s an equal chance of each song being played each time. Until 2014, that’s how the shuffle function worked, but people complained that it wasn’t random enough. So, Spotify changed it.
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How Spotify Shuffle works
When you press the “Next” button, Spotify doesn’t randomly select the next song right then and there. The next song has already been decided by the time you activated shuffle mode.
The name “shuffle” is actually a very accurate description of how it works. Think of it like shuffling a deck of cards. When you tap the shuffle button on a playlist, all the songs are shuffled in a new order. This happens every time you click the shuffle button.
You can see this if you check the queue. I made a playlist of 10 songs, half of which are by the same artist, and shuffled it five times. Spotify generated a new song order each time. Even in this small sample size, you can clearly see some of the issues people are complaining about.
The same song was at the top of the list the first two times I shuffled around, that’s more “random doesn’t feel random”. More importantly, the artist that appears on the playlist five times is never evenly distributed. In fact, in two of the shuffles four of the five songs were grouped together.
This is how Spotify shuffle works on a basic level, but again, this isn’t random. Spotify stopped using true random in 2014. Now there is an algorithm that decides the random play.
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enter the algorithm
Fortunately, a Spotify engineer described exactly how the algorithm works on the Spotify Engineering blog in 2014. The algorithm has almost certainly been tweaked since then, but it’s surprisingly simple.
First, the algorithm distributes songs by the same artist. However, it intentionally doesn’t always do it perfectly, as seen above, to maintain a sense of randomness. Generally, they will appear every 20-30% of the duration of the playlist.
The algorithm also mixes songs by the same artist together. This is to prevent songs from the same albums from playing too close together. Artists that only appear once in the playlist are “shuffled” to prevent them from always being at the top of the playlist.
That is all! The algorithm itself is quite simple. keep a feeling of randomness is what really complicates things. If shuffling always arranged artists perfectly the same distance from each other, it would feel like a repeating pattern. Shuffle has to strike a balance between true randomness and manufactured randomness.
random is hard
There are more advanced music shuffle algorithms. The problem is that adding complexity can make algorithms slower. Spotify’s algorithm is simple, but that allows you to shuffle almost instantly.
The human brain makes the concept of “random” difficult to execute. The algorithm is more about creating the mirage of randomness than true randomness because that’s what our brain wants. The system is never going to be perfect, but you can always hit the shuffle button one more time.
If you’re still curious about this topic, check out this great video by Gabi Belle on YouTube.