GA4 Identity: The Reporting Identity Setting Explained
One admin setting decides how confidently GA4 can say "this is the same person" across devices - and most teams have never opened the screen where it lives.
In short
Admin > Reporting identity controls which signals GA4 is allowed to use, in what order, to decide whether two hits belong to the same person: User-ID (if you send one) first, then Google signals (if enabled and consented), then device ID as the fallback. Blended uses all three; Observed uses User-ID and device ID but not Google signals; Device-based uses device ID only. The setting doesn't touch your event data - it changes how that data gets stitched into user counts, so a change here can move reported user totals with nothing else different.
What the Setting Controls
| Setting | Signals used, in order | Requires |
|---|---|---|
| Blended | User-ID → Google signals → device ID | Google Signals enabled + user consent for cross-device features to actually engage |
| Observed | User-ID → device ID | Nothing extra - the default fallback hierarchy without Google signals |
| Device-based | Device ID only | Nothing - simplest, most conservative option |
Whichever level is selected, GA4 always falls back to the next available signal if a stronger one is missing for a given hit - a logged-out visitor with no User-ID sent still gets counted, just by device ID instead.
Why It Changes Your Numbers
Every level above Device-based tries to merge multiple device IDs into one person, which by definition reduces the reported user count relative to raw device counts, assuming any real cross-device behavior exists in your traffic. Google Signals also introduces its own reporting thresholds on some demographic and interest dimensions, which can cause otherwise-visible data to show as withheld once Blended is enabled and enough signal-based traffic qualifies.
Worth checking, not assuming: the exact threshold values Google applies for signal-based data suppression are not published as fixed numbers and can vary by property size - treat any specific figure you've seen elsewhere as an approximation, not a guarantee, and verify against your own property's behavior. [hypothesis - Google does not publish exact thresholds]
Choosing a Setting on Purpose
- Choose Blended if cross-device journeys matter to how you report and you already run Google Signals for remarketing - you're already collecting the signal, so use it for identity too.
- Choose Observed if you want User-ID-based stitching for logged-in users without opting into Google Signals' broader data-sharing implications.
- Choose Device-based if you want the most conservative, least-inferred number - every device-browser pairing counted once, no merging assumptions.
Whichever you pick, document it - the setting is easy to change and easy to forget was changed, and a shifted user count with no corresponding tracking change is confusing to explain months later without that record.
Frequently Asked Questions
What does GA4's Reporting Identity setting actually change?
It changes the hierarchy GA4 uses to decide whether two hits belong to the same user - User-ID first, then Google signals, then device ID, versus a narrower hierarchy that skips one or more of those. Switching it changes user counts and can change which sessions get grouped together in a user's journey, without changing your event data itself.
Why did my user count change when I didn't touch the tracking code?
The Reporting Identity setting can be changed independently of any tag or tracking-code change, and it directly affects deduplication across devices. If user counts moved but events look stable, check this setting before assuming a tracking bug.
Is Device-based identity more accurate than Blended?
Neither is universally "more accurate" - they measure different things. Blended attempts to unify a person across devices using every available signal, which can undercount unique people if signals are missing, or merge two different people who share a device. Device-based counts every device-browser combination as distinct, which avoids that merging risk but treats one person on two devices as two users.
Not Sure Which Identity Setting Fits Your Property?
We walk through what your property already sends and recommend a setting based on what you're actually trying to measure.
Get GA4 Identity HelpGet GA4 Identity Help
Tell us what changed in your user counts, and whether Google Signals is currently on.