Identity Resolution platforms link fragmented customer records across owned data, partner networks, and digital touchpoints into unified person, household, or account graphs that downstream marketing and advertising systems can act on. Core capabilities include deterministic and probabilistic matching of identifiers (email, phone, device, account), B2B account-to-individual graph stitching, second-party data collaboration via clean rooms, and audience activation. The market spans B2B-focused vendors (LiveRamp, FullContact), B2C and retail-focused vendors (Acxiom, Neustar, Epsilon), and identity infrastructure providers (Trade Desk Unified ID 2.0, ID5).