What is a lookalike audience?
A lookalike audience is a targeting segment of new people who resemble an existing group, called the seed audience. The seed is usually your best customers or engaged site visitors. A platform analyzes what the seed has in common, such as interests, behaviors and demographics, and finds other users with similar profiles who have not interacted with you yet.
Lookalikes are sometimes called similar or modeled audiences. They are one of the main ways to grow beyond your own first-party data without falling back to broad targeting.
How lookalike audiences work
Choose a seed: upload a customer list or select a pixel-based audience, for example everyone who bought in the last 90 days.
Model: the platform's algorithm compares seed users with its wider user base and scores each user by similarity.
Set the size: many platforms let you choose between a tighter, more similar audience and a larger, looser one.
Target and refresh: the lookalike is used as an audience segment and updated as the seed and user data change.
Each platform handles this differently. Some offer explicit lookalike segments with a size setting. Others use automated audience expansion that finds similar users during bidding, guided by conversion signals rather than a fixed list.
Seed quality decides result quality. A seed of high-value repeat customers produces a more useful lookalike than one built from every visitor who left after a few seconds.
Why lookalike audiences matter
Efficient prospecting: you reach new people who are more likely to convert than a random audience.
Scale from small data: a modest customer list can be turned into a much larger target pool.
Less reliance on cookies: when built from logged-in platform data and consented customer lists, lookalikes keep working where third-party cookies are blocked.
Clear testing: you can compare lookalikes of different seeds, such as high spenders versus all buyers, to learn which customer type is worth chasing.
Two habits help: exclude existing customers from the lookalike so you pay only for new reach, and watch frequency, because small, tight lookalikes saturate quickly. It also pays to refresh seeds regularly, since a lookalike built on last year's buyers drifts as your product, pricing and customers change.
Lookalike audience vs retargeting
Retargeting reaches people who already visited your site or engaged with your brand. A lookalike audience reaches people who have not, but who look like those who did. Retargeting usually converts at a higher rate but has a small ceiling. Lookalikes feed the top of the funnel, so there is more to retarget later. Many advertisers run both with separate budgets and goals, so prospecting results are not mixed up with retargeting conversions.
Lookalike audiences with AdGeeks
AdGeeks traders build lookalike and audience expansion strategies on Amazon DSP, DV360 and Adform, using the options each platform supports. We help pick the right seed, set exclusions, and compare lookalike performance with contextual and in-market audiences during optimization.
