In a data clean room, each party contributes data to a shared environment and agrees in advance on which queries may run and which results may leave it. Participants see aggregated outputs, such as counts or overlap rates, rather than each other’s customer-level records. Typical controls include minimum group sizes for any result, limits on query types, and sometimes differential privacy noise added to outputs.
Advertising measurement is the best-known use. A retailer and a brand can measure how many people who saw a campaign later bought the product, and neither side hands over its customer list. Clean rooms also appear in healthcare research and financial services. They make data sharing possible under strict rules, and the rules also limit what the analysis can return, so partners agree upfront on the questions the analysis must answer.