Amazon, Disney and Hershey’s offer data clean rooms – as do a growing roster of media companies, cloud providers, adtech purveyors and prominent brands. The clean rooms enable companies to share consumer data with each other for targeted marketing while purportedly protecting privacy. Caveat emptor: the technical approaches to clean rooms vary. This article discusses types of clean rooms and looming regulatory questions. It also provides questions to ask while vetting these offerings, with insights from a Frankfurt Kurnit partner and speakers at the Interactive Advertising Bureau’s annual meeting. See “Ad Industry’s Third-Party Data Use Grew Despite Impending Cookie Shutdown” (Feb. 23, 2022).