What is A/B Testing? — UK Software Development Guide

4 min readJune 2025ClickMasters Technical TeamReviewed by James Whitmore, CTO
what is ab testing software

Direct Answer

A/B testing (split testing) is a method of comparing two versions of a product, feature, or content to determine which performs better. Users are randomly assigned to version A (control) or version B (variant). Statistical analysis determines whether the observed difference in a metric (conversion rate, click-through rate, engagement) is statistically significant or likely due to chance.

Ab-testing in the UK

A/B testing has specific UK GDPR implications. A/B testing that involves processing personal data (user IDs, behaviour tracking) requires a valid legal basis — typically legitimate interest for product improvement analytics. UK GDPR and PECR: if A/B testing uses cookies to assign users to variants, cookie consent is required for non-essential cookies. FCA Consumer Duty: A/B testing dark patterns (deliberately showing a worse option to a control group) is prohibited — A/B tests on FCA-regulated interfaces must both variants provide fair treatment. ICO guidance: A/B testing constitutes automated processing that may require a DPIA if it affects users significantly.

Get Expert Advice on Ab-testing

Speak with our UK software development experts about Ab-testing. Free consultation, transparent pricing, no obligation.