What is the north star metric for Duolingo, in your view?

“I want to separate habit from learning. Daily use is easy to measure, but the real value is getting better at a language, so I'll pick a metric and say where it falls short.”

Try answering out loud for a few minutes before you open this.

1. State the value: learning a language in small daily steps
2. Candidates: daily active users, lessons completed, skill progress
3. Pick daily active learners and explain the reason
4. Admit the gap: activity is not the same as learning
5. Pair with a learning-quality check, such as test score gains
6. Name inputs: streak retention, lesson completion, notification response