Reporting Identity

Reporting identity is the setting that tells GA4 how to combine signals into a single user across sessions and devices.

You choose from three options in admin. Blended uses User-ID first, then falls back to device signals and modeling to estimate users. Observed uses User-ID and device ID without modeling. Device-based ignores everything except the cookie or client ID on that browser, counting each device as its own user.

The same person visits on two devices without logging in. Under device-based, GA4 reports two users. Under blended, GA4 may model them into one, which lowers your total user count but describes the actual audience more accurately. Switching the setting does not change collection; it only changes how the existing data is counted.

The setting is retroactive and applies to reports, not raw data. Flip from device-based to blended and your historical user numbers shift too, because GA4 recalculates on read rather than storing one fixed count. Since Google removed Signals from the identity in 2024, the practical choice is mostly blended versus device-based, and blended is the default for a reason.

Same data, different arithmetic. The setting decides who counts as one person.