Definition
Incremental ROAS is return on ad spend calculated only against the revenue a campaign actually caused - the incremental revenue measured by an experiment - rather than all revenue the campaign was credited with by an attribution model. If a campaign is credited with 100,000 in revenue but a holdout test shows only 30,000 of that would not have happened without it, the attributed ROAS is on 100,000 and the incremental ROAS is on 30,000, a very different and much lower figure.
iROAS is the honest version of ROAS. It requires an incrementality experiment (a geo or audience holdout) to establish the causal revenue, so it cannot be produced from a dashboard, but it is the number that actually tells you whether a channel is worth its spend.
In context
For iGaming advertisers, iROAS is the metric that resolves the recurring gap between what attribution says a channel earns and what it actually contributes. Attributed ROAS in this vertical is systematically inflated: last-click over-credits brand search and coupon affiliates, view-through over-credits display, and retargeting gets credit for conversions that would have happened anyway.
Running incrementality tests to get iROAS reveals which channels are genuinely productive at the margin and which are harvesting existing demand at a good-looking but misleading attributed ROAS.
The practical use is to periodically validate the biggest spend lines with holdouts, express their return as iROAS, and reallocate toward channels with strong incremental returns and away from those whose attributed ROAS does not survive the test. It pairs with MER as the top-line check and with media-mix modelling for the strategic view.
For affiliates, iROAS is the operator-side rationale behind incrementality-based deal decisions: an affiliate whose traffic tests as genuinely incremental - new players who would not have arrived otherwise - supports a higher rate, while one whose apparent value is mostly intercepted demand will see its deal cut when the operator measures iROAS. For affiliate-facing content, the framing is that incremental ROAS measures return against only the revenue a campaign caused, established by an experiment, that it is typically much lower than attributed ROAS which over-credits in this vertical, that it is the honest basis for budget and deal decisions, and that an affiliate delivering genuinely incremental players is what a good iROAS depends on.
Worked example
An operator's brand-search campaign shows an attributed ROAS of 8. A geo holdout finds pausing it costs only a small fraction of the credited revenue, giving an incremental ROAS closer to 1.5. The operator cuts brand-search spend sharply and moves it to a prospecting channel whose holdout shows a much stronger iROAS.
Related terms
Frequently asked questions
Browse more iGaming terms in our glossary.
← Back to glossary