What are “post-click” vs “post-open” conversions?
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When someone converts after receiving your email, how you measure that conversion depends on which event you tie it to: the click or the open.
Post-click conversions are counted when a reader clicks a link in your email and then completes a desired action, like making a purchase or filling out a form. This is the most reliable method because a click is a deliberate action you can actually track end-to-end with UTM parameters.
Post-open conversions count actions taken after an open event, even without a click. Think of unique coupon codes: if you give each subscriber a different code, you can attribute a purchase to an email open even if no link was clicked. This approach made more sense before 2021. But Apple's Mail Privacy Protection (MPP) changed everything. MPP pre-fetches emails and fires open tracking pixels automatically, which means millions of "opens" are now triggered by Apple's servers, not real humans. Any open-based attribution built on that data is now unreliable for audiences with significant Apple Mail usage.
Today, post-click attribution is the safer default. If your model relies on opens, segment your analysis by email client first and treat Apple Mail opens as noise. For e-commerce specifically, unique coupon codes or dedicated landing page URLs per campaign can bridge the gap when clicks aren't available.
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