Essence
Product metrics turn "is the product doing well" from feeling into measurable numbers for decisions. The key: pick metrics that reflect real user value, not vanity metrics that grow nicely but mean nothing (downloads ≠ users).
North Star Metric
One metric reflecting the product's core user value, e.g. "Shorts published per week". Good NSM grows only when users get value.
AARRR
Acquisition · Activation (the "aha" moment) · Retention · Revenue · Referral.
HEART
Happiness · Engagement · Adoption · Retention · Task success — each via Goal → Signal → Metric.
Base metrics
DAU/MAU (stickiness), activation rate, retention curve (D1/D7/D30), time-to-value.
Worked example
MAU = 10,000; DAU = 2,000; new signups = 3,000; reached first value = 1,200; D7 returns = 540.
Stickiness = 2,000/10,000 = 20%. Activation = 1,200/3,000 = 40%. D7 retention = 540/3,000 = 18%.
Lever: activation 40% — half don't reach value. Simplify onboarding → lower time-to-value → raise activation → lifts retention & NSM.
When to use
North Star for team focus; AARRR for growth/funnel; HEART for UX quality.
Pitfalls
Vanity metrics; North Star = revenue; ignoring retention (leaky bucket); averages without cohorts; a metric with no action.