PostHog — Open Source Product Analytics & Session Replay

Introduction

PostHog is an all-in-one, open-source product analytics platform that replaces multiple SaaS tools. It provides event analytics, session recordings, feature flags, experiments, and a built-in data warehouse — all self-hostable so your data never leaves your infrastructure.

What PostHog Does

• Tracks product events and visualizes funnels, retention, and user paths
• Records user sessions with full DOM replay for debugging UX issues
• Manages feature flags and runs A/B experiments with statistical analysis
• Provides a built-in data warehouse to join external data sources
• Offers an SQL query editor for ad-hoc analytics on raw event data

Architecture Overview

PostHog runs on Django and React with ClickHouse as the analytics database for fast OLAP queries. Kafka handles event ingestion, and PostgreSQL stores metadata. Session recordings are stored on object storage (S3 or MinIO). The stack is orchestrated via Helm on Kubernetes for production deployments.

Self-Hosting & Configuration

• Deploy with the official Helm chart on Kubernetes for production scale
• Use Docker Compose for smaller teams or evaluation setups
• Configure ClickHouse retention policies to manage storage costs
• Set up reverse proxy with TLS termination via Nginx or Caddy
• Environment variables control database connections, object storage, and email

Key Features

• Unified platform replaces Amplitude, Hotjar, LaunchDarkly, and Segment
• Auto-capture SDK instruments clicks, page views, and inputs without manual code
• Correlation analysis automatically surfaces properties linked to conversion or drop-off
• Group analytics lets you track organizations and accounts, not just individual users
• Open-source core with a permissive MIT license for self-hosted deployments

Comparison with Similar Tools

• Amplitude — powerful analytics but cloud-only SaaS; PostHog is self-hostable
• Mixpanel — event analytics without session replay; PostHog bundles both
• Plausible — privacy-focused page analytics; PostHog covers full product analytics
• Matomo — web analytics oriented; PostHog adds feature flags and experiments
• Heap — auto-capture analytics but proprietary; PostHog is open-source

FAQ

Q: Is PostHog free to self-host? A: Yes, the open-source edition is MIT licensed. PostHog Cloud offers a generous free tier as well with paid plans for higher volumes.

Q: How much data can it handle? A: ClickHouse scales horizontally. Production users process billions of events per month on self-hosted clusters.

Q: Can I migrate from Amplitude or Mixpanel? A: PostHog provides import scripts and an API to ingest historical event data from other platforms.

Q: Does it support mobile apps? A: Yes. Official SDKs exist for iOS, Android, React Native, and Flutter alongside web SDKs.

Sources

• https://github.com/PostHog/posthog
• https://posthog.com/docs