What is Google Signals in GA4?
Google Signals is a GA4 setting that enriches your data using information from signed-in Google users who have ads personalisation on. It unlocks cross-device tracking and demographics, but it comes with privacy strings and a well-known side effect.
What it gives you
- Cross-device: it can link a user across phone and desktop when they are signed into Google, so journeys are less fragmented.
- Demographics and interests: age, gender and interest data in reports.
- Better remarketing reach through Google's signed-in network.
The privacy trade-offs
Because it relies on personal data from signed-in users, Signals has consent implications, and in strict EU interpretations many sites leave it off or gate it behind consent. It is not something to switch on without thinking about your consent position.
The side effect: thresholding
Turning Signals on is a common trigger for GA4 data thresholding, where GA4 hides small numbers to protect individual identity. If reports started showing "data withheld" after you enabled Signals, that is why. Weigh the cross-device benefit against the reporting gaps before enabling it.
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