CRO Toolbox

A/B switcher, Datalayer reader, test analyser, MDE calculator & SRM checker for Convert.com, VWO, Varify, Kameleoon, Optimizely

CRO Toolbox is a Chrome extension for CRO consultants, online marketers, and anyone involved in A/B testing. It opens as a side panel next to the website you're working on and gives you a set of tools to support your testing workflow — from QA on live sites to planning and analysing experiments. It’s designed to stay open while you browse, so you can inspect experiments, track events, and run calculations without constantly switching tabs or re-opening popups. What’s included A/B Switcher — rebuilt from the ground up Quickly inspect and switch variants for running experiments directly on the page you’re viewing. Shows experiment names and variant names instead of just technical IDs, so it’s much easier to know which test you’re looking at. Detects when something is a live deployment rather than an actual A/B test, so you won’t accidentally try to switch to a variant that doesn’t exist. Supports multiple experimentation platforms and handles common implementation quirks. Supported platforms: Kameleoon support — detects and switches variants for experiments running on Kameleoon, including cookie-based assignment and experiment discovery from the Kameleoon JavaScript object. Optimizely Web support — full support for Optimizely Web experiments, including detection via the Optimizely data object, variant switching, and forced activation. VWO, Convert.com & Varify — detection and experiment-handling logic for all three platforms has been overhauled for reliability. Handles edge cases around async script loading, anti-flicker snippets, and multi-experiment pages more robustly. Currently supports Convert.com, VWO, Varify, Kameleoon, and Optimizely Web. DataLayer Reader — real-time event inspection Inspect every event pushed to the dataLayer in real time while you browse. Live streaming view — see new events as they’re pushed, without refreshing the page. Automatic grouping — events are grouped into GTM, Ecom, GA4, and Others tabs so you can cut straight to the signals that matter without scrolling through noise. Smart tagging — automatic tagging for GA4, ecommerce, and GTM events. Filtering & grouping — filter by keyword, group events by type, and keep a per-page history so you can see exactly what fired where. Ideal for QA’ing tracking before, during, and after a test. A/B Analyzer — significance, explained clearly Paste in your visitors and conversions and get a clear, practical interpretation of your test results. Choose between two analysis approaches depending on how you like to work. See the probability that your variant is winning. Get the expected uplift and a plain-language interpretation of the result so stakeholders can understand the outcome without statistical jargon. MDE Calculator — minimum detectable effect Understand what size of impact your test can realistically detect. Calculates the smallest improvement your test would be able to reliably detect, week by week, based on your site traffic. Helps you decide how long to run a test before the results are meaningful. Useful for planning realistic expectations with stakeholders and avoiding underpowered tests. SRM Checker — Sample Ratio Mismatch detection Check whether your test traffic was actually split as intended. Paste in your visitor counts per variant. Get an instant verdict on whether there is a Sample Ratio Mismatch (SRM). See a per-variant breakdown so you can diagnose issues with traffic allocation that might make results unreliable, even when the headline numbers look promising. Sample Size Calculator — plan before you test Figure out how many visitors you need per variant before you start a test. Estimate the required sample size per variant based on your baseline rate, expected uplift, and desired confidence. Helps you avoid ending a test too early or running it much longer than necessary. Aligns expectations with stakeholders on timeline and traffic requirements. What’s new in v1.5.0 Kameleoon support added — variant detection and switching for Kameleoon experiments, including cookie-based assignment and discovery from the Kameleoon JavaScript object. Optimizely Web support added — full support for Optimizely Web experiments, including detection, variant switching, and forced activation. VWO, Convert.com & Varify detection overhauled — more robust handling of async script loading, anti-flicker snippets, and pages with multiple experiments. DataLayer Reader improved — events are now automatically grouped into GTM, Ecom, GA4, and Others tabs so you can focus on the events that matter most. CRO Toolbox was previously known as A/B Experiment Variant Switcher, but has grown well beyond simple variant switching. The new name reflects its broader scope as an all-in-one side panel for A/B testing workflows.