Deterministic attribution matches an ad click to an install using a unique device identifier, giving you a certain (not estimated) answer about which ad drove which install.
Deterministic attribution uses a unique, persistent device identifier to create an exact match between an ad interaction and a conversion. On Android, this identifier is the GAID (Google Advertising ID). On iOS, it's the IDFA (Identifier for Advertisers). When a user clicks an ad and later installs the app, the MMP checks whether the device ID from the click matches the device ID from the install. If they match, attribution is certain.
This is the gold standard of mobile attribution because there's no guesswork involved. One device, one click, one install. The match is deterministic: either the IDs match or they don't.
Apple's ATT framework, introduced in iOS 14.5, significantly reduced the availability of IDFA on iOS. Users must now explicitly opt in to allow tracking. With industry opt-in rates sitting at 25 to 45%, the majority of iOS installs can no longer be attributed deterministically. Android retains broader deterministic coverage through GAID, though Google has signaled plans to introduce similar privacy controls with Privacy Sandbox.
Deterministic attribution is the most accurate way to know your creative and campaign performance. When you have it, your CPI, ROAS, and LTV numbers are based on verified install-to-ad matches, not statistical estimates. Losing deterministic coverage on iOS (post-ATT) is why probabilistic attribution and SKAN have become necessary, and why MMP data for iOS campaigns now requires careful interpretation rather than face-value reading.
Example
“A user clicks a Meta ad on their iPhone (IDFA: abc-123) and installs the app the next day. AppsFlyer records the click with IDFA abc-123 and matches it to the install event from the same device. That's deterministic attribution: a certain, verifiable match.”
Probabilistic attribution assigns conversion credit to ad exposures based on statistical likelihood rather than deterministic device identifiers.
Learn moreMobile AttributionATT is Apple's iOS framework that requires apps to request explicit user permission before tracking their activity across other companies' apps and websites.
Learn moreMobile AttributionSKAdNetwork is Apple's privacy-preserving mobile attribution framework for iOS, which reports campaign-level install and conversion data without revealing individual user identity.
Learn moreMobile AttributionAn MMP is an independent third-party platform that attributes app installs and in-app events to the advertising sources that drove them.
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