A/B testing (also called split testing) is the practice of comparing two versions of a webpage, email, ad, or other marketing element to determine which one performs better. Version A is the control (what you currently have) and Version B is the variant (what you want to test). Traffic or sends are split between the two versions, and the winner is determined by whichever version drives more of the desired outcome - higher conversion rate, more clicks, more revenue per visitor.
A/B testing is the systematic alternative to intuition-based decisions. Without it, marketers rely on opinion to determine whether a different headline, image, CTA button, or layout performs better. With it, actual user behaviour becomes the judge. For Shopify brands, A/B testing is the most reliable way to improve conversion rate because it controls for confounding variables - changes in traffic volume, seasonality, or campaign mix - that would otherwise make performance comparisons unreliable.
The highest-value A/B test targets are: product page headline and hero image (the two elements with the most outsized impact on add-to-cart rate), CTA button text and colour, shipping and return policy display placement, social proof format and position (star rating prominence, review display style), and free shipping threshold messaging. A/B testing of landing pages is particularly valuable because paid traffic has direct cost - each incremental conversion improvement reduces CPA proportionally.
An A/B test is only trustworthy if it achieves statistical significance - typically 95% confidence - before declaring a winner. Most tests require at least 1,000 conversions per variant and a minimum of two full business weeks to control for day-of-week effects. Testing tools with Shopify integration include Google Optimize (deprecated), Intelligems (revenue-focused Shopify tests), and Replo. Heatmaps and session recordings complement A/B testing by explaining why a variant outperforms - what users are clicking, where they are dropping off, which page elements they are engaging with most.
Klaviyo's native A/B testing for subject lines, sender names, send time, and email content is one of the most accessible and high-impact optimisation activities in email marketing. Even small subject line improvements of 3-5 percentage points in open rate compound significantly across a large list - and email A/B tests typically reach statistical significance faster than site tests because lists are large and conversion events (opens, clicks) are frequent.
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