Experiments

    Superhuman's PMF engine (annotated case study)

    Validated

    Context

    In 2018, Rahul Vohra published a detailed account of how Superhuman used a single survey question — 'How would you feel if you could no longer use Superhuman?' — to quantify and then engineer product-market fit. The framework is a canonical example of turning an intuition ('users seem to love this') into a falsifiable, repeatable measurement. Source: First Round Review, 'How Superhuman Built an Engine to Find Product/Market Fit.'

    Hypothesis

    The percentage of users who would be 'very disappointed' to lose a product is a leading indicator of durable product-market fit; a team can move that number deliberately by focusing on the users who almost love the product and the features they most cite.

    Kill criteria

    As published: if the 'very disappointed' segment did not grow in response to focused iteration on their stated blockers, the framework would not be a usable engine — just a snapshot metric.

    Validation criteria

    Superhuman's reported 'very disappointed' share rose from 22% to 58% over roughly four quarters while the team deliberately built for the segment that almost loved the product. The framework has since been reproduced by dozens of teams with public write-ups.

    Signals observed

    Baseline reading: 22% of active users said they would be 'very disappointed' without Superhuman — below Sean Ellis's ~40% threshold associated with sustainable growth.

    2018-11First Round Review

    After segmenting the 'somewhat disappointed' cohort and shipping against their specific blockers, the 'very disappointed' share reached 58% — above the threshold, and sustained.

    2019First Round Review

    Outcome

    Validated as a repeatable technique. Cited here as a canonical example of turning a vibe ('people seem to love it') into a signal (a single survey question) into a validation loop (iterate against the almost-love cohort). Read the original: firstround.com/review/how-superhuman-built-an-engine-to-find-product-market-fit.

    Created: 2026-07-05

    Updated: 2026-07-18