Author of Hacking Growth · Coined "Growth Hacking" Head of Growth at Dropbox & Eventbrite · LogMeIn founding team
SEP 5 2024
The PMF Test
The Sean Ellis Test: One Question that Changes Everything
"How would you feel if you could no longer use this product?" — Ask only active users who've used it 2+ times within the last 2 weeks.
Focus entirely on the "very disappointed" group — they're your must-have users
Ignore "somewhat disappointed" — they signal a nice-to-have, not a must-have
40% is a guideline, not a law — culture and category affect the number
It's a leading indicator; retention cohorts are the true final measure
Minimum ~30 responses before treating the score as reliable
Framework
From PMF Signal to Scalable Growth Engine
40%
PMF threshold
30
min responses
2wk
recency window
Deeply understand who your must-have users are and why before you scale anything
North Star Metric = a unit of must-have value delivered. Not revenue — Amazon uses monthly purchases, Airbnb uses nights booked
Acquisition is the last priority — fix conversion and retention first or ad spend simply won't scale
Blend qualitative (surveys, calls) with quantitative (cohort data, A/B tests) — experiments get dramatically better when rooted in customer context
Lookout case study
7% PMF score → repositioned entirely on antivirus + streamlined onboarding to lead with "you're now protected." Score hit 40% in 2 weeks, 60% in 6 months. Became a unicorn.
Deep Dive
Speed to Value: The Activation Obsession
The LogMeIn 10× activation story
95% of signups never completed a single remote control session — the actual product use
CEO froze the entire product roadmap; all of product, engineering, and design shifted to activation only
3 months later: signup-to-usage improved from 5% → 50%
Same acquisition channels that had maxed at $10K/mo now scaled to $1M/mo
80% of new users came through word of mouth after the fix — organic flywheel kicked in
"A problem well stated is a problem half solved." — Kettering (Sean's favourite quote). Most activation problems vanish once the right question is asked.
Two universal conversion levers
1. Increase desire — remind users of the benefit they're about to receive at every step. 2. Reduce friction — ruthlessly cut every step between signup and aha moment.
Ask why they dropped off
LogMeIn had 90% drop at download. After 10+ failed A/B tests, they simply emailed non-downloaders "what happened?" Answer: "seemed too good to be true — I didn't believe it was free." Added a paid-trial option beside free → 300% lift in download rate.
Find your aha moment
Start qualitatively: what's the earliest moment a user genuinely feels value? Then confirm with data — does reaching that moment correlate with long-term retention? If yes, optimise relentlessly for speed to that moment.
Tactics
Mine the Must-Have Cohort
Step 1 — Open-ended: "What is the primary benefit you get?" Crowdsource raw language from very-disappointed users
Step 2 — Multiple choice: Turn top answers into 4 benefit options; send to a different group of very-disappointed users and force a pick
Step 3 — Context: "Why is that benefit important to you?" — this unlocks acquisition copy. Xobni users said "I'm drowning in email." That became the ad hook.
Step 4 — Alternatives: "What would you use instead?" Must-have users struggle to answer; nice-to-have users name substitutes instantly
Superhuman twist: For somewhat-disappointed users who value the same core benefit, ask what's missing — move them up without diluting the core
Nubank's evolution
Uses the Sean Ellis test down to the feature level. New features must hit 50% before public launch. Sean wasn't involved — they adopted it independently.
Contrarian
Growth Myths Sean Ellis Kills
✗Drive acquisition first to learn fastINSTEAD →✓ Fix activation and retention first. Pouring traffic into a leaky funnel burns budget without building anything. Acquisition channels won't scale until conversion is efficient.
✗A referral program creates word of mouthINSTEAD →✓ Referral programs are an accelerant, not a spark. Dropbox had strong organic sharing before the incentive program launched. It can't fix a product no one talks about.
✗Revenue should be your North Star MetricINSTEAD →✓ Measure units of value delivered — nights booked, monthly purchases, weekly rides. Revenue is a byproduct of doing that well. Teams optimising revenue directly tend to shortcut value creation.
✗40% PMF score means you're ready to scaleINSTEAD →✓ PMF is only the starting line. You still need to understand who your must-have users are, build the activation loop, and prove retention cohorts — only then does acquisition spend pay off.