S2S postback vs pixel firing — choose by attribution risk

S2S postback vs pixel firing — choose by attribution risk

A conversion can report two ways. They are not interchangeable. Decide by where the conversion happens.

Use S2S (server-to-server) postback when:
— Conversion fires server-side (deposit, sale confirmed in network backend).
— You can't trust the user's browser (ad-blockers, app environments, cookie loss).
— You need iOS/Safari-proof attribution.

Use pixel (client-side) when:
— Conversion is a browser event you control (button click, thank-you page).
— The advertiser only offers a pixel, no postback URL.
— You need same-session retargeting data.

Failure modes to weigh:
— Pixels lose 5-20% to blockers and early-exit; S2S loses 0% but needs a click ID round-trip.
— S2S requires the network to store and return your click_id — if they drop it, you get null conversions.
— Pixels can double-fire on refresh; dedupe by transaction ID.

Rule: money events → S2S. Engagement events → pixel. Never trust a pixel for revenue.

Save this SOP. Run this before every launch.