~/learn/Product Metrics · Funnels & cannibalization
Cannibalization
When a new feature grows by taking usage from existing ones — and how to measure net impact.
why this matters
Meta, Google and Spotify interviewers love asking how to evaluate a new surface fairly.
Cannibalization happens when a new feature's success comes from pulling users away from another part of the product rather than creating new value. Instagram Reels views might grow while Feed views shrink by a similar amount; a cheaper plan might attract existing customers who downgrade.
The question to answer is always the net effect: did total value (time spent, revenue, satisfaction) go up across the whole product? A controlled experiment compares the whole ecosystem between groups, not just the new feature's numbers.
Net impact
new feature usage +100
old feature usage −80
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net ecosystem impact +20 ← this is what mattersInterview trap
Reporting 'Stories got 500M views in week 1' without asking where those views came from is the classic mistake. Interviewers want you to ask about the rest of the product.
Pro tip
Some cannibalization is fine — even strategic — if the new surface monetizes better or defends against a competitor. Say that out loud: it shows business judgment.
key takeaways
- New usage may come from old features.
- Measure net impact on the whole product.
- Some cannibalization can be strategic.
check your understanding
A new Shorts tab gets 50M daily views. What's the first thing to ask?