CPA, or cost-per-action or cost-per-acquisition on Facebook, is the cost you pay when someone visits your website after clicking on a Facebook ad. Cost per action (CPA) allows you to only pay for actions (lead generation, page likes, video views app installs and link clicks) that people take as a result of your ad. CPA measures your success in connecting with your Facebook audience. A high CPA indicates that your campaign is not successful, whereas a low CPA indicates that you are on the right track.