Retargeting

Retargeting shows ads specifically to people who have already visited a site, opened an app, or engaged with a brand in some tracked way, rather than to a cold audience. A user who viewed a product page without buying, for example, might later see an ad for that same product on a different site, driven by an audience list built from that earlier visit.

Retargeting depends on being able to recognize a returning user, historically through a cookie dropped on their earlier visit, which is one reason the shift toward cookieless tracking has forced advertisers to rely more on logged-in identifiers, server-side signals, and platform-native audience matching. It is the mirror image of lookalike audience targeting, which finds new prospects who resemble existing customers rather than re-engaging people who have already shown interest.

Retargeting matters because it typically converts at a higher rate than prospecting to cold audiences, since it targets people with demonstrated intent rather than unknown interest. Its main pitfall is over-frequency: without frequency capping, the same retargeting ad can follow a user for weeks after they lost interest or already bought elsewhere, which wastes spend and can damage brand perception through the site the ads appear on, delivered largely via programmatic advertising.