What is Lookalike Audience?
An ad-targeting audience the platform builds by finding new users who resemble a source list of your existing customers or high-value events, such as purchasers or add-to-cart users. On Meta you choose a percentage size from 1 to 10 percent of a country's population, where 1 percent is the tightest match and larger percentages trade precision for reach. TikTok offers an equivalent Lookalike feature built from a custom-audience seed.
A lookalike (Meta's term; TikTok calls it the same, and the general concept is an act-alike or similar audience) is only as good as its source. A seed built from actual purchasers or high-LTV customers produces a far stronger audience than one built from page views or broad engagement, so the highest-quality available event should feed it. The standard practice is to start narrow at 1 percent for the cleanest match, then expand to 2 to 5 percent or stack multiple percentage tiers once a campaign needs more reach to spend. Over the past few years platform automation (Meta's Advantage+ and broad targeting) has reduced reliance on manually built lookalikes, since the delivery system increasingly finds buyers on its own when fed strong creative and conversion signals. Even so, lookalikes remain a useful lever for seeding new campaigns and giving the algorithm a quality starting population. Crucially, audience targeting cannot rescue weak creative: on paid social the hook and ad body still decide whether a well-matched viewer stops, watches, and clicks.
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