Best Practices for A/B Testing

Running an A/B test is just the start — getting meaningful results depends on how you set up your experiments. These best practices will help you run more effective tests, avoid common pitfalls, and get clearer insights from your data.

Test one variable at a time

It can be tempting to change multiple things at once, but doing so makes it hard to know which change actually influenced performance. If you swap a headline, image, and call-to-action in the same test, you won’t know what moved the needle.

To get reliable insights, focus on one clear change per test, whether it's a headline, a layout adjustment, or a new button style. This simplifies analysis and makes it easier to apply learnings elsewhere.

Focus above-the-fold improvements

The area users see before they start scrolling, often called “above the fold”, is where attention is highest and decisions are often made. It's also where small changes can have an outsized impact.

Testing elements like headlines, hero images, featured products, or calls-to-action in this space tends to produce faster and more meaningful results. These are also the first elements users see on mobile, making them doubly important.

Optimizing for mobile

With most traffic now coming from mobile devices, it’s essential to preview and prioritize mobile performance during your test setup. Layouts that look great on desktops may not translate well to smaller screens, leading to skewed results.

When designing your variants, always ensure they are mobile-responsive. Keep touch targets large enough to tap easily, avoid stacked buttons, and ensure key content appears early in the scroll.

Testing trust elements (reviews, badges, return policies)

Customers look for signs that a store is reliable and secure, especially if they're new to your brand. Testing the placement, style, or presence of trust elements, such as customer reviews, secure checkout icons, return policies, or satisfaction guarantees, can have a significant influence on conversions.

Try surfacing these elements earlier on the page, or testing different styles (e.g., badges vs. text) to see which builds more confidence.

Iteration & follow-up tests

A single test can tell you what worked best this time, but ongoing iteration is how you make lasting improvements. After one variant wins, consider running a follow-up test to refine that version even further, maybe by testing a different headline or adjusting supporting content.

Testing isn’t one-and-done. The more you build it into your workflow, the more insights you'll uncover and the more confident you’ll be in your design and messaging decisions.