The best Optimizely alternatives & competitors, compared
Contents
1. PostHog
- Founded: 2020
- Similar to: VWO, LaunchDarkly
- Typical users: Engineers and product teams
- Typical customers: Mid-size B2Bs and startups

What is PostHog?
PostHog (that's us 👋) is an open-source platform that includes A/B testing, feature flags, product analytics, session replay, and user surveys. This means it's also an alternative to tools like Mixpanel (product analytics) and Hotjar (session replay and surveys).
Typical PostHog users are engineers and product managers at startups and mid-size companies. Customers include Supabase, ElevenLabs, and Airbus.
According to BuiltWith, as of April 2024, 5,610 (0.5%) of the top 1 million websites use PostHog. This is slightly more than Optimizely's 5,353.
Key features
Feature flags: Safely rollout features with local evaluation (for faster performance), JSON payloads, and instant rollbacks.
A/B tests: Up to 9 test variations, primary and secondary metrics. Automatically calculate test duration, sample size, and statistical significance.
Product analytics: Funnels, user paths, retention analysis, custom trends, and dynamic user cohorts. Also supports SQL insights for power users.
Surveys: Target surveys by event or person properties. Templates for net promoter score (NPS), product-market fit (PMF) surveys, and more.
Session replays: Including event timelines, console logs, network activity, and 90-day data retention.
How does PostHog compare to Optimizely?
The core of feature flags and experimentation are similar between the two. The big difference is that PostHog is free, open-source, and has analytics built in, while Optimizely has a range of enterprise content, commerce, and collaboration tools.