(Source) When someone is looking to test pages or designs against each other to see how well they convert on a website, they’ll use CRO tools. CRO stands for Conversion Rate Optimization, and the idea is that you run variations of a page against each other to see which one converts the best. While this may not seem like it can make a difference, it does, and that’s why companies like Facebook use A/B testing CRO tools to analyze site usability. Likewise, Amazon uses A/B testing to complete the checkout process as seamlessly as possible.