Optimizely sells Feature Experimentation and Web Experimentation on custom, MAU-based plans. Pages here cover replacing them with self-hosted GrowthBook, or PostHog where analytics comes along.
Optimizely Feature and Web Experimentation against self-hosted GrowthBook: flags and SDKs, stats engines, warehouse-native analysis, the visual editor on GrowthBook's paid tiers, what the free self-hosted plan includes, and the effort of running GrowthBook yourself.
For product teams that want experiments next to product analytics and session replay: Optimizely against self-hosted PostHog, what PostHog's free deployment is sized for, the lack of support for self-hosted PostHog, and when GrowthBook is the better experimentation choice.
Moving from Optimizely to GrowthBook without a built-in importer: inventorying flags and experiments, recreating them through GrowthBook's API, swapping SDKs or the web snippet, rebuilding metrics on your warehouse, and checking results against the Optimizely events export before cutover.
Cost of ownership by component: Optimizely's individually packaged plans billed on MAUs, where Web Experimentation counts every visitor on a page with the snippet, against GrowthBook's free or Enterprise self-hosted plan, servers and MongoDB, warehouse query costs, migration and the people to run it.
What leaves Optimizely and how: the daily Parquet Experimentation Events Export, its one-year retention, the end of S3 delivery on November 30, 2026 and the GCS-only rule for EU customers, plus flag and experiment configuration you need to capture before the contract ends.
Replacing the Optimizely Web snippet for marketing and CRO tests: GrowthBook's visual editor and script tag, which plans include it, its limits on client-side-rendered apps, how MAU counting changes, and when flag-based experiments in code are the better fit.
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