Case study: a depositor-only lookalike halved cost-per-FTD

Case study: a depositor-only lookalike halved cost-per-FTD

What it is: A buyer fed broad lead lists to ad platforms for lookalike seeding. Switching the seed to confirmed-depositors-only (passed back via the broker's conversion API) reshaped who the platform targeted.

Best for: Buyers who can pass FTD events back to the ad platform's conversion API.

What was done:
— Replaced a 50,000-lead seed audience with a 1,900 confirmed-depositor seed
— Passed FTD events back via the platform's conversion API for ongoing optimization
— Ran both seeds in parallel for 4 weeks on equal budget

Outcome:
— Cost-per-FTD on the depositor-seed audience came in 48% lower
— Lead volume dropped, but lead-to-FTD rate nearly doubled
— The platform's optimization compounded as more FTD events fed back

Pros:
— A small clean seed beat a huge dirty one decisively
— Conversion-API feedback let the platform self-improve toward depositors

Cons:
— Needs broker cooperation to pass FTD events back accurately
— A 1,900-person seed is near the minimum; smaller seeds get unstable

Who should skip this: Buyers who can't get FTD events back from the broker — you can't seed what you can't measure.

Verdict: Seed on depositors only.