OptiPilot

The community resource for Optimizely practitioners. Implementation guides, troubleshooting tips and best practices by David Sertillange, an independent experimentation specialist with 10 years implementing Optimizely across enterprise programs.

This site is not affiliated with, endorsed by, or sponsored by Optimizely. Optimizely is a trademark of Optimizely, Inc. This is an independent developer project.

Getting Started

New to Optimizely? Choose your path to get started.

Feature Experimentation

Server-side A/B testing, feature flags, and targeted rollouts

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Web Experimentation

Client-side A/B testing for websites without code changes

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Integrations

Connect with Google Analytics, Segment, and more

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Start here by problem

The questions practitioners arrive with most often, and the guide that answers each one.

My variation flashes before it rendersHow to Prevent the A/B Testing Flicker Effect in Optimizely WebFix the A/B testing flicker effect (FOOC) in Optimizely Web: diagnose the slow stage, apply the cheapest fix first, and verify it under real conditions.Read the guideMy MAU count is higher than expectedOptimizely MAUs: What Counts as a Monthly Active User & How to Reduce OveragesWhat counts as a Monthly Active User (MAU) in Optimizely, how MAUs are counted, and step-by-step fixes to diagnose and reduce MAU overages on your bill.Read the guideOptimizely and GA4 disagreeExperiencing a Google Analytics data discrepancy with Optimizely? Here's how you can fix itFix Google Analytics data discrepancies with Optimizely by aligning how each tool tracks experiment events, so your numbers reconcile across both platforms.Read the guideMy traffic split looks wrongSample Ratio Mismatch: Is Your A/B Test Broken?Your traffic split looks off and results feel wrong. Learn to detect sample ratio mismatch with a chi-square test, find the cause, and fix it.Read the guideI do not know when to stop the testHow Long Should You Run an A/B Test? A Practical GuideHow long should you run an A/B test? Learn to size the sample, convert it to days, cover a full business cycle, and when you can stop early.Read the guideI cannot tell what the results page is sayingHow to Read the Optimizely Results Page CorrectlyHow to read the Optimizely results page: statistical significance, confidence intervals, and the common gotchas that lead experimenters to the wrong conclusion.Read the guide

Free tools

Calculators and checklists that run in the browser. No signup, no email wall.

Experiment QA ChecklistPre-launch checklist with 27 validation items across 7 categories.A/B Test Sample Size CalculatorCalculate required sample size and estimate how long your experiment needs to run.Statistical Significance CalculatorEnter visitors and conversions per variation to get a two-tailed p-value, a confidence interval on the lift, and a plain verdict.Experimentation Velocity CalculatorFind out how many A/B tests your team can realistically run per year.Stats Method PickerNot sure which Optimizely stats engine to use?Sample Ratio Mismatch (SRM) CheckerEnter observed visitors per variation and get a chi-square p-value that tells you whether your traffic split is broken — the essential pre-analysis validity check.CUPED Variance Reduction EstimatorEstimate how much traffic and time CUPED saves your experiment from the correlation between pre- and in-experiment metrics.Feature Flag Naming Convention GeneratorDescribe a flag and get a clean, consistent, searchable key in your chosen convention — across dot, kebab, snake, and screaming styles — plus naming discipline that scales.A/B Test Prioritization ScorerRank your test backlog with the ICE or PIE framework.Bulk Targeting SimulatorRun thousands of user profiles through an Optimizely datafile and inspect variation splits, audience matches, and rule funnels without firing impressions.
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The Mission

After years of implementing Optimizely across dozens of client projects, I’ve encountered nearly every edge case, integration challenge, and "gotcha" the platform has to offer. This site exists to share those hard-won lessons with the community.

The official Optimizely docs are comprehensive, but sometimes you need practical, real-world examples. You need to know why your MAU count is higher than expected. You need to understand how to properly forward GA4 events. You need the context that only comes from hands-on experience.

That’s what OptiPilot delivers: practical implementation guides, troubleshooting tips, and best practices from real-world Optimizely deployments.

About the Author

David Sertillange is an independent experimentation specialist with 10 years implementing Optimizely across enterprise programs. He specializes in Feature Experimentation, analytics integrations, and helping teams build a culture of data-driven decision making.