What is an identity graph?
An identity graph is a database that links the different identifiers belonging to the same person or household, such as email addresses, phone numbers, cookies, mobile ad IDs and connected-TV IDs, so advertisers can recognize them across devices and channels. Links are either deterministic, based on logins, or probabilistic, inferred from signals like IP address and device.
Identity graphs power cross-device targeting, frequency capping and measurement. Deterministic matching relies on the same login across devices; probabilistic matching estimates connections and is less accurate. Providers include LiveRamp, Experian, TransUnion and many data companies.
Privacy laws and platform rules constrain them. Apple restricts fingerprint-like linking under App Tracking Transparency, and practices such as ID bridging, where a probabilistic match is passed off as a deterministic one, have drawn industry criticism.