Verdict
Settle on last-click because networks measure it reliably, but steer with first-click and incrementality data. Otherwise you structurally overpay cashback and underpay content.
What last-click measures
Last-click assigns the commission to the final affiliate click inside the tracking window. It is simple, undisputed and therefore the default in nearly every network.
The downside: partners close to the purchase, such as cashback and coupon sites, take the commission even when a content partner created the demand.
What first-click measures
First-click rewards the partner who introduced the visitor. That fits review and comparison sites working early in the journey.
The downside: a first click without follow-up says little about purchase intent, and the model is more exposed to low-quality reach.
What works in practice
Most mature programmes keep paying on last-click but add a second layer: bonuses or higher rates for partners who demonstrably bring new customers.
That keeps administration simple while the incentives stay correct.
How to test the difference
Pause a publisher group temporarily and measure what happens to total revenue. If it stays flat, that group was harvesting rather than adding.
Combine that with a path report from your network showing which partners appear more often as assists than as the last click.