Duolingo's most powerful re-engagement notification is one sent after five days of inactivity stating, "these reminders don't seem to be working. We're going to stop sending them." This passive-aggressive message makes users feel the app is "giving up on them," which is surprisingly effective at getting them to return.

When facing a "brick wall" where user perception contradicts data (e.g., feeling ad load is high when it's low), incremental changes fail. The solution is to re-architect the experience from first principles. This can unlock growth in key metrics like ad load while simultaneously improving user satisfaction.

As businesses scale, they often abandon the scrappy, creative tactics that sparked their initial growth. To combat rising ad costs and channel fatigue, intentionally revisit these early, 'unscalable' activities. Re-injecting that fun, different energy can generate the 'free memories' and reach needed for the next growth phase.

To amplify word-of-mouth, Duolingo identified existing sharing behavior by temporarily tracking user screenshots. They found hotspots like streak milestones and funny challenges, then invested in designers to make these moments even more shareable.

For a mature product, a key growth lever can be removing identity friction. By allowing users to bring their existing accounts (e.g., Gmail) instead of forcing a new one (e.g., Yahoo.com), you lower barriers, solve the 'cold start' problem, and can dramatically increase adoption by delivering immediate value.

To grow an established product, introduce new formats (e.g., Instagram Stories, Google AI Mode) as separate but integrated experiences. This allows you to tap into new user behaviors without disrupting the expectations and mental models users have for the core product, avoiding confusion and accelerating adoption.

Figma learned that removing issues preventing users from adopting the product was as important as adding new features. They systematically tackled these blockers—often table stakes features—and saw a direct, measurable improvement in retention and activation after fixing each one.

The most durable growth comes from seeing your job as connecting users to the product's value. This reframes the work away from short-term, transactional metric hacking toward holistically improving the user journey, which builds a healthier business.

Because AI products improve so rapidly, it's crucial to proactively bring lapsed users back. A user who tried the product a year ago has no idea how much better it is today. Marketing pushes around major version launches (e.g., v3.0) can create a step-change in weekly active users.