Cross-device

Cross-device is a technology and analytical approach that allows you to link the actions of the same user on different devices (smartphone, tablet, desktop) into a single path. Without cross-device attribution, analytics sees “three different users” where there was one person.

The problem is real: the user saw an advertisement on a smartphone → opened the site on his work computer → bought it in the evening from his home laptop. In “standard” analytics, the conversion will be attributed to the last touch from a laptop (direct entry), and an advertising campaign on a smartphone will not receive “credit.” CPL will be underestimated, ROAS will be distorted.

Cross-device identification methods: deterministic (login on a website or application - the most accurate), probabilistic (comparing IP, user agent, behavioral patterns - less accurate, ~70–85% accuracy). Google and Yandex use their login data for deterministic matching - users authorized in Chrome or Yandex Browser are reliably identified.

In my practice, cross-device is especially important in MMP for mobile applications and in complex B2B funnels with long transaction cycles. For small e-com projects, standard analytics with sufficient accuracy - the main thing is not to forget about this limitation when interpreting the data.