How Duolingo Reignited User Growth

A detailed case study of Duolingo's growth team and how they rebuilt user growth through a sequence of experiments and structural changes — push notifications, the streak mechanic, activation funnels, a new model of experimentation.

The piece is worth reading not for its specific tactics (which are Duolingo-specific and often replicated badly) but for the underlying shift it documents: growth as a disciplined, continuous practice rather than a one-off campaign.

For product direction the most useful takeaway is organisational — Duolingo built a team structure and a decision cadence that made growth work legible, which is rarer than the tactics themselves.

Lenny's Newsletter is full of this kind of reporting; this is one of the sharpest pieces.