Notes on ProductNotes on Product
Notes on Product

Product ideas
worth stealing.

We study exceptional companies and pull apart the decisions, mechanics and tiny details behind how they build, grow and keep users.

One sharp teardown each week. No fluff.

Latest note
Duolingo · Retention · 05.22.26
Fig. 01 — Habit Loop

Duolingo — Retention Playbook

Pick one north-star behavior. Build every system — UI, notifications, social, monetization — around protecting it.

~32%
DAU/MAU ratio
~8.5%
Paid conversion
60+ days
Avg streak (engaged users)
13M+
TikTok followers
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The Notebook

10 companies dissected so far

01LinearLinear — Brand Playbook
Notes, delivered

Steal one useful product idea every week.

We do the digging. You get the interesting bit.

One useful idea. Occasionally several.

What we study

You've reached the end.

We spend an unreasonable amount of time studying products so you don't have to.