FTD (First Time Deposit) marks the moment a signup becomes a paying player. It is the standard acquisition conversion metric and the basis of almost every affiliate CPA deal.
The trap with FTD is treating it as a synonym for customer. A cohort with many minimum-value FTDs can have worse LTV than a smaller cohort with a higher average deposit. When CPA triggers on a minimum deposit, the incentive sent to the affiliate is to generate exactly that profile, it is not bad faith, it is the criterion that was written.
Mature operations track FTD alongside three cuts: first deposit value, time to second deposit, and D30 cohort retention. The latter two predict value far better than raw FTD volume.
It is also common to define a qualified FTD, a deposit above a floor with minimum activity, to align acquisition payments with real traffic quality.