What is a lookalike audience
Also known as: lookalike segments, lookalikes, similar audiences
A lookalike audience is an audience an ad platform builds from a seed list, such as customers or website visitors, by gathering people with similar characteristics. It is used to reach new people who resemble existing buyers. In Google Ads, lookalike segments only exist in Demand Gen campaigns and, since March 2026, are shifting to work as a suggestion rather than a constraint.
A supplement store has 3,000 customers who bought more than once. It uses that list as the seed for a lookalike audience and advertises a first purchase bundle to it.
Instead of targeting everyone interested in fitness, the campaign first reaches people who resemble returning customers. Cost per first purchase comes in below the open campaign, and new customers' repeat rate looks like the original list's.
How it works
Result quality depends on the seed list. A list of repeat buyers says far more about the ideal customer than a list of everyone who signed up for a promotion.
- The company provides a seed list: customers, repeat buyers or visitors to a page.
- The platform analyzes what those people have in common.
- It builds an audience of similar people who are not yet on the list.
- The campaign targets that audience, which can be adjusted from more similar to broader.
What Google changed in 2026
Google Ads is moving lookalike segments in Demand Gen campaigns to a suggestion mode, in phases throughout 2026, starting in March. The seed list becomes a signal for Google's models, and the system may reach people outside the similarity thresholds if that helps the campaign goal, such as conversions or cost per action.
As a result, the reach slider of narrow, balanced and broad, which used to limit the audience to 2.5%, 5% or 10% of the chosen location's population, no longer works as a constraint. Advertisers who prefer the previous behavior can opt out through a form, and Google says interface controls will come later.
Meta and other platforms
Meta offers lookalike audiences for Instagram and Facebook ads, and other platforms have similar features. The logic is the same: start from a list of valuable people to find others like them. Size and control details vary from platform to platform.
Cautions
- Use lists with proper consent and legal basis, as privacy laws require.
- Prefer lists of valuable customers to lists of sheer volume.
- Keep the list current; customers from three years ago may not represent today's customer.
- Compare the lookalike audience with an open campaign to know whether it really performs better.
Frequently asked questions
What is a lookalike audience?
An audience an ad platform builds with people similar to those on a seed list, such as customers or website visitors.
Where are lookalike segments available in Google Ads?
According to Google, only in Demand Gen campaigns.
What changed in Google's lookalike segments in 2026?
Since March 2026, they are shifting to a suggestion mode: the seed list becomes a signal, and the system may reach people outside the similarity thresholds to meet the campaign goal.
Which list should I use as the seed?
Your most valuable customers, such as repeat buyers or those with higher order values. Volume lists without criteria produce less precise audiences.
Do lookalike audiences require consent?
The seed list is made of personal data, so it needs a proper legal basis under privacy laws and must follow each platform's policies.
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Rodrigo Fávaro
Founder of ROO3, a marketing and technology agency in São José do Rio Preto, Brazil. Builds AI products running in production (Tobia, gerar.app, Pense Mercado) and maintains the AI Benchmark, a public ranking of AI models.
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