Lookalike Audience

A lookalike audience is a group of new users a platform selects because they resemble an existing audience you provide, such as your best customers.

The quality of a lookalike is entirely dependent on the quality and size of the source audience (the "seed"). A lookalike built from your top 1,000 highest-LTV customers will generally outperform one built from every visitor who ever loaded your homepage, because the algorithm is pattern-matching against a much more meaningful signal.

Google's version is called "similar audiences" and has been deprecated on some surfaces in favor of broader, signal-based automated targeting (Performance Max, Advantage+) — a sign of the industry-wide shift described in audience targeting.