THE MOTHER OF ALL PERSONALIZED PLAYLISTS HITS MILESTONE

Spotify's innovative Discover Weekly personalized playlist has drawn 40 million unique users since launching in July—that’s more than half of the service’s claimed 75m active users—while that vast constituency has streamed north of 5 billion tracks. The company made the announcement Wednesday.

Significantly, more than half of Discover Weekly’s users save at least one of the 30 songs that appear every week, listen to at least 10 tracks and come back the following week. The 25-to-34 age group is using it the most, which Spotify’s lead engineer Ed Newett explained to Tech Crunch is because in “the years after college…it’s not as easy to discover music.”

The playlist disappears each Monday, replaced by a new one, but according to Newett, Spotify is looking at a possible Discover Weekly Flashback feature or some other option to recover your old song sets.

"Discover Weekly started as a hack project, and if 10 other people had hack ideas, we didn’t have the resources to push them out," Matt Ogle, who helps lead development of music discovery and personalization at Spotify, told The Verge. "The update to the infrastructure will allow us to experiment a lot more. We can now do this kind of deep personalization at scale across a number of different products."