What a Funnel Is, and When It Fits
A funnel is an ordered sequence of instrumented steps toward a single outcome. At each step you count how many users made it, and the shrinkage between steps is the drop-off. Signup, onboarding, checkout, and upgrade flows are the classic cases: bounded, mostly linear, with one clear finish line.
Bounded, ordered path to one outcome
Checkout, signup, onboarding, KYC, upgrade. Steps are discrete and instrumented.
Open-ended or compounding journeys
Browsing behavior, long multi-channel journeys, or growth that feeds itself, use a journey map or a growth loop.
It's worth knowing what a funnel is not. A journey map covers emotion and context across touchpoints; a funnel only counts. A growth loop lets output feed back into input; a funnel is strictly one-directional, so it can never model compounding. And a funnel answers where users leave, never why.
Quick check
A PM builds a funnel with the steps "visited site", "was interested", "signed up". What's the defect?