A call-to-action (CTA) is a button or graphic on a website that prompts users to click in order to continue down a conversion funnel. The main goal of a CTA is to get clicks, and its success can be measured by a conversion rate formula. CTAs can also be tested using A/B testing to determine the most effective design. Common types of CTAs include calls to sign up, register, call, subscribe, or donate. CTAs work best when they communicate offers with a sense of urgency and limited availability. The placement, design, and wording of CTAs can significantly impact conversion rates.