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Reference library · Cross-media measurement
Identity Resolution / Identifier Interoperability
Identity resolution is the process of matching device- and platform-specific identifiers — cookies, mobile ad IDs, CTV device IDs, logged-in IDs — to a common person- or household-level key so exposure across channels counts once instead of once per device. Identifier interoperability is the share of those identifiers that actually resolve to a shared key across two or more data sources. A planner reads it as a match rate: the percentage of an audience that can be reconciled across platforms, not a guarantee that the whole audience is covered.
Formula
Worked example
A buyer sends 5,000,000 hashed emails from a CTV partner's inventory into a match against a DSP's 12,000,000-ID graph. 2,150,000 of the CTV IDs resolve to an ID already in the DSP graph. Match rate = 2,150,000 / 5,000,000 x 100 = 43%. That means 43% of CTV exposure can be reconciled with the DSP's audience for a deduplicated cross-media reach count; the remaining 57% either gets excluded from the unified reach figure or falls back to probabilistic modeling.
How it is used
Planners check the match rate before trusting a cross-media deduplicated reach number from a clean room or ID graph vendor, since a low rate means the 'unified' figure is built mostly on modeled overlap rather than deterministic links. The rate is also used to compare vendors, but only after confirming both quote it against the same denominator — matched over the smaller platform's pool gives a very different number than matched over the combined union.
The common mistake
Don't read a high match rate as audience coverage; it measures how much of the audience could be deduplicated, and the matched slice skews toward logged-in, cookie-permissive users rather than representing the full audience.