Cost per action or CPA marketing, also known as cost per conversion and pay per action (PPA), is an advertising model where the publishers are paid for each specified action such as double opt-in, form submit, click, and impression.

This is different from common affiliate marketing methods in a way that you do not have to make sales to earn.

Payments are based on lead generation like submitting an email address or phone number to get some information or free products. CPA is considered by direct response advertisers as the optimal way to purchase online advertising because advertisers pay for the advertisement when the desired action is performed.