Probabilistic attribution
Probabilistic attribution matches an install to a click by comparing device and network characteristics both events carried, when no identifier passes through the store to link them directly.
It's the fallback layer: used when neither an install referrer nor a click token is available. Because it infers rather than observes, an honest report keeps probabilistic matches separate from deterministic ones.
Comparing device characteristics is device fingerprinting, which needs end-user consent under the ePrivacy Directive and is restricted by Apple. LinkTrail's version is off by default, consent-gated, and compares only the IP address and platform — the methodology page documents it.