Multiple slots and interaction detection

liftstack supports testing multiple content positions (slots) within the same campaign. For example, you can test subject lines and hero blocks simultaneously.

How multi-slot testing works

Each slot is tested independently. Recipients are assigned variants for each slot using full factorial assignment, meaning all combinations are tested. This ensures clean attribution of results to individual content decisions.

Interaction detection (Scale tier)

On the Scale tier, liftstack can detect interactions between slots. An interaction occurs when the effect of one slot depends on another, for example, an urgency subject line might perform better when paired with an urgency hero block. Interaction detection identifies these patterns and reports them alongside individual slot verdicts.