A/B testing in affiliate marketing is a method of testing two different versions of a marketing campaign to determine which version yields the best performance. This type of testing is used to evaluate elements such as headlines, images, and call to action buttons in order to determine which variation results in the highest click-through rate, conversion rate, or overall performance.For example, an affiliate marketer may create two versions of an email campaign to promote a product. The first version may feature a headline that reads "Buy Now - 50% Off!" while the second version may feature a headline that reads "Check Out Our Big Sale - 50% Off!". The marketer would then send both versions to their email list and measure how many people clicked through to the landing page and how many sales were generated from each version. Based on the performance of each version, the marketer can then decide which version of the email campaign to use going forward.