What Is Incrementality Testing? A Practical Guide
Written by Elias Oender
May 28, 2026 1 min read
The quick answer
Incrementality testing measures the true impact of marketing efforts by isolating their effect. It uses methods like holdout and geo tests to compare outcomes with and without campaigns. This approach often beats trusting platform-reported conversions, especially when accuracy is critical.
What Is Incrementality Testing?
Incrementality testing is a method to measure the true impact of marketing campaigns by isolating their effect. It answers the question: Would conversions have happened without the campaign? Unlike platform-reported metrics, which often attribute conversions broadly, incrementality testing focuses on the actual lift generated. This approach is particularly useful when skepticism about attribution accuracy is high. For example, if you’re unsure whether your marketing attribution model reflects reality, incrementality testing can provide clarity.
How Do Holdout and Geo Tests Work?
Holdout tests divide your audience into two groups: one exposed to the campaign and another held back as a control. By comparing outcomes, you measure incremental lift. Geo tests, on the other hand, target specific geographic areas while leaving others untouched, allowing for a broader comparison. Both methods are powerful but require careful planning. For instance, geo tests work best when markets are similar enough to ensure valid comparisons. If you’re unsure which method suits your needs, consider starting with a free marketing scan.
When Is Incrementality Testing Worth It?
Incrementality testing is worth the effort when platform-reported conversions may be biased or inflated. For example, if your campaigns rely heavily on retargeting, platform metrics might overstate their impact. Incrementality testing can also help you optimize your marketing budget by identifying high-performing strategies. However, it’s not always necessary. For smaller campaigns or when precision is less critical, platform-reported data might suffice. If you’re ready to explore incrementality testing further, book a quick call to discuss your strategy.
