PostHog

PostHog is an open-source, all-in-one product analytics platform. It combines event analytics, session replay, feature flags, A/B testing, and user surveys in a single tool. Self-host on your own infrastructure or use PostHog Cloud—either way, you own your data. With autocapture, SQL access, and a warehouse-native architecture, PostHog gives engineers and product teams complete visibility into user behavior without vendor lock-in. Generous free tier makes it accessible for startups and side projects.