Why does the audience size in GA4 not match Google Ads?

The audience size in Google Analytics 4 (GA4) often differs from what’s shown in Google Ads due to a range of technical, consent, syncing, and eligibility differences. While GA4 may include users based on analytics data, Google Ads only counts users who meet specific remarketing and personalization criteria. Table of Contents How does user … Why does the audience size in GA4 not match Google Ads?