Zero-party data
Data a customer intentionally and proactively shares with a brand — preferences, intentions, profile attributes.
Zero-party data is information a customer intentionally and proactively shares with a brand: preferences, intentions, profile attributes, communication preferences, declared interests. The term distinguishes from first-party data (behavior observed by the brand on its own properties), second-party data (another brand's first-party data shared via partnership), and third-party data (purchased from a broker).
Zero-party data is the most valuable type for email personalization because it's both highly accurate (the customer said so) and legally clean (consent is built into the collection). Preference centers — where subscribers self-select interests, cadence, and content types — are the canonical zero-party data collection tool. Onboarding quizzes and personalization wizards are the modern alternatives.
The mechanics of using zero-party data: every collected attribute should map to a content variant or segment. Asking "what topics interest you?" only matters if subsequent sends actually filter or vary based on the answer. Collecting zero-party data without acting on it not only wastes the data but trains subscribers that their preferences don't matter, reducing the rate at which they'll fill in future preference centers.