Ad Optimization is performance-enhancing technology that is used to boost the click-through-rate (CTR) of a Pay-Per-Click (PPC) ad on search engines. Ad Optimization may come stand-alone as a plug-in or add-on, integrated into an A/B Testing tool for campaign performance, or built into powerful Ad Servers that are programmed to report impressions and clicks, post-click and post-impression activities, and interaction metrics. (See also A/B Testing: Ad Campaign Performance).