The Owl That Came Back on Day Forty

Duolingo's innovation was never the teaching. It was working out that the entire product is whether somebody opens it again tomorrow — and then running its social media on exactly the same principle.

Language courses were expensive and dull, and most people who bought one stopped within a fortnight. Duolingo made one that was free, and then spent a decade on a problem the incumbents had never treated as a problem at all: getting somebody to come back on day forty.

The streak counter, the leaderboard, the notifications from an increasingly desperate green owl. It is easy to be sniffy about all of it. It is also the only reason anybody is still learning Portuguese in week six.