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What is A/B Testing? Definition, Examples, and Website Analytics Use Cases

A/B testing is a controlled experiment where you show different versions of a page, product flow, message, or feature to different groups of visitors. Version A is usually the control, while version B is the variation. The goal is to measure which version performs better against a specific outcome, such as signups, purchases, trial starts, email clicks, or activation events.

In web analytics, A/B testing connects design and product decisions to evidence. Instead of choosing a headline, call to action, pricing layout, or onboarding step by opinion, you track how real visitors behave.

How A/B testing works

An A/B test starts with a hypothesis. For example, "Changing the hero button from View demo to Start free trial will increase signup conversion rate." Traffic is split between the control and the variation, and each visitor is assigned to one version so their experience stays consistent.

The analytics platform then tracks outcomes for both groups. Common test goals include:

  • Click-through rate on a call to action
  • Signup conversion rate
  • Checkout completion
  • Feature adoption
  • Revenue per visitor
  • Error rate or page speed impact

The strongest tests measure one primary goal and a few guardrail metrics. Guardrails matter because a variation can improve clicks while hurting product quality, retention, performance, or revenue.

Why A/B testing matters

A/B testing is useful when a decision can affect a measurable outcome and the page or flow receives enough traffic to produce a stable result. It is especially valuable for landing pages, pricing pages, signup flows, checkout pages, onboarding steps, and product launches.

Good A/B testing also prevents false confidence. A one-day traffic spike or a few enthusiastic users can make a change look better than it is. A proper test keeps the comparison fair by splitting traffic and measuring the same goal over the same period.

A/B testing and privacy

Privacy-friendly A/B testing should avoid invasive profiling. You do not need third-party cookies or cross-site tracking to run useful experiments. In Swetrix, experiments can be connected to analytics goals and custom events, so you can measure variants while keeping tracking lightweight and privacy-first.

Related terms: conversion rate, custom event, funnel, and call to action.

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