How does Google determine user location and how accurate is it?

Almost everything else in GA4 is first party, meaning that you are tracking things that happen on your website. But demographics are third party data, meaning this is something Google infers based on its overall profile of your visitors across the internet. It’s a black box but the likely data points are:

• People’s Google/YouTube accounts
• Third party advertising cookies
• Visiting websites that do share anonymous demographic data with Google

You can see what categories Google thinks you fall into for the purposes of advertising in My Ad Center.

Ad blockers, deleting cookies and incognito browsing all stop this reporting, and these days most websites would probably have less than 25% of their visitors count in demographic reports.

If these aren’t coming through, you’ll need to enable Google Signals. If they’re enabled but you don’t see data, Google is redacting these reports for privacy reasons because it doesn’t include enough users. You can sometimes get around this by extending the date range, but Google won’t show any row of data that has too few users.

Dimensions to check out

• Age: There are 6 age brackets. Google will not report demographic data for anyone it thinks is under 18.
• Gender: Because these fields are all based on large sets of users, this just has the basic male and female buckets (as well as unknown).
• Interests: This is based on people’s browsing profile outside of your website. It will be noisy!

Things to watch out for

Don’t over-infer from demographic data! In addition to not being very accurate, it’s easy to start using it to revert to stereotypes and truisms. Like with geographic data, the most actionable thing might be comparing engagement and conversion rates across different demographics, since the total audience makeup per demographic bucket often depends on your marketing.