~/learn/Product Metrics · Engagement, retention & churn
DAU, WAU, MAU & stickiness
Count active users correctly and use DAU/MAU to measure how habit-forming a product is.
why this matters
DAU/MAU is the go-to engagement ratio at social and consumer companies.
Daily, weekly and monthly active users (DAU, WAU, MAU) count distinct users who did a meaningful action in that window. The hard part is defining 'active': opening the app, or actually doing the core action (sending a message, watching a video)? A strict definition is harder to inflate.
Stickiness is DAU ÷ MAU: on an average day, what share of this month's users show up? Messaging apps can reach 50%+. A tax app might sit at 5% — and that's fine, because people only need it occasionally. Always judge stickiness against how often the product is naturally needed.
Stickiness = DAU / MAU Example: 300k DAU / 1.2M MAU = 25% → the average user is active ~7.5 days a month
Reading stickiness
strict 'active' definition → honest number DAU/MAU high → daily habit (chat, social) DAU/MAU low → occasional need (travel, taxes) compare to natural usage frequency, not to Facebook
Interview trap
MAU can grow while DAU/MAU falls — lots of new users who try it once and leave. Always look at both the size and the ratio.
Pro tip
Use 'L28' style histograms (how many users were active 1, 2, … 28 of the last 28 days) to show whether you have a core of power users or mostly drive-by visitors.
key takeaways
- Define 'active' strictly.
- Stickiness = DAU / MAU.
- Judge it against natural usage frequency.
check your understanding
An app has 200k DAU and 1M MAU. What is its stickiness?