Mixpanel

Suhail Doshi and Tim Trefren built it in 2009 out of Y Combinator. The pitch was a rebellion against Google Analytics' page-view model: track discrete events ("purchased", "shared", "uninstalled") and ask afterwards how they chain into funnels, cohorts and retention curves. Its data model — events carrying arbitrary properties — became the template the whole product-analytics industry copied.

Pricing has swung back and forth; a generous free tier in 2022 was a direct answer to Amplitude and the open-source upstart PostHog eating share from below. Still privately held, unusual for its age.