Definition
A/B testing compares two versions of a page or element by showing each to a random share of visitors and measuring which produces more conversions.
A/B testing explained
In an A/B test, version A is the current page and version B changes one thing, such as the headline, the offer, the form length or the CTA. Visitors are randomly split between them, and once enough data has been collected, you compare conversion rates to see whether the difference is real or just chance.
Reliable tests need:
- A clear hypothesis based on research, not a random idea.
- Enough traffic and conversions to reach statistical confidence.
- A fixed duration, usually covering full weeks, rather than stopping as soon as one version looks ahead.
- One primary metric agreed in advance.
Testing tools can slow pages down if they load heavy scripts or hide content while deciding which version to show, which hurts LCP and INP. Server-side testing avoids this. For SEO, Google says not to show Googlebot different content from people, to use canonical tags on alternate test URLs, to use 302 rather than 301 redirects for tests, and to remove test elements once a test ends.
Example
Your landing page headline talks about features. You A/B test it against a headline about the outcome customers want. After several weeks with a sample large enough to trust, the outcome-led version produces more enquiries, so it becomes the new default.
Why it matters
A/B testing replaces opinions with evidence, so conversion improvements are real and can build on each other.
Related service
Landing Page Development
Fast, focused landing pages for ads and campaigns, built to be tested and improved.
Landing page development servicesSources
- Google Search Central: Minimize A/B testing impact in Google Search (updated 10 Dec 2025)
Published by Vidern, founded and led by Malhar Shah. Updated .
Need a hand with your site?
Tell us about your site and we'll reply within 1 business day.
Related terms
- CRO (Conversion Rate Optimization)CRO (conversion rate optimization) is increasing the share of visitors who take a desired action, such as buying, booking or submitting a form.
- Conversion rateConversion rate is the percentage of visitors or sessions that complete a goal, such as a purchase, sign-up or enquiry, out of all visitors or sessions.
- Landing pageA landing page is a page built to turn visitors from a specific campaign or search into leads or customers, with one clear goal and call to action.
- CTA (Call to Action)A CTA (call to action) is the prompt, usually a button or link, that tells visitors what to do next, such as “Book a demo” or “Get a quote”.