Plan, debug, and ship better experiments

Free planning tools, Chrome DevTools diagnostics, and practical Optimizely playbooks—built by David Sertillange, an independent experimentation specialist with 10 years implementing the platform.

Find your fix Explore the Chrome extension

Web + Feature Experimentation · No signup · No email wall

The OptiPilot toolkitFree · No account

Plan + validateQA and statistics toolsSize, prioritise, QA, and read experiments.10 free tools DebugChrome DevTools companionExplain live decisions on the page.13 diagnostics ImplementPractical guidesFix integrations, flicker, data, and rollout issues.Step by step

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Integration articles

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Practical guides

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Start with the problem in front of you

Choose the symptom you recognise and go straight to the practical diagnosis.

Problem 01My 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 guide Problem 02My 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 guide Problem 03Optimizely 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 guide Problem 04My 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 guide Problem 05I 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 guide Problem 06I 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

OptiPilot Companion

Debug Optimizely without reconstructing the story

Add a purpose-built panel to Chrome DevTools and see why a visitor received a variation, where tracking broke, and what happened before the result you are looking at.

Explain the decision

Trace bucketing, audiences, holdbacks, and feature-flag rules.

Catch broken tracking

Validate events, tags, duplicates, and decision order as they happen.

Share the diagnosis

Export a redacted bundle instead of sending a screen recording and guesswork.

Explore the Chrome extension

Free · No OptiPilot account · No analytics or telemetry

An experiment’s variation detail and bucketing decision inside the OptiPilot DevTools panel

Experiment detail: the variation this visitor received, and the draw that produced it.

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Free experimentation tools

Make the statistical and QA decisions that slow teams down. Everything runs in your browser.

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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.

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Why OptiPilot exists

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.

David Sertillange

Independent experimentation specialist

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.