CPA is an affiliate commission model where the advertiser pays only when a user completes a specific action — typically a purchase, subscription signup, lead form submission, or app install. The affiliate bears all traffic-acquisition risk; the advertiser pays only for verified results.
CPA is the dominant model in performance affiliate marketing because it aligns incentives cleanly: publishers optimize for quality conversions, not just clicks. Common CPA rates range from $2–$5 for lead generation to 20–40% of the first payment for SaaS subscriptions. Networks like Commission Junction, Impact, and PartnerStack facilitate CPA tracking between advertisers and publishers.