Glossary
What is a Lookalike Audience?
A Lookalike Audience is a group of people Meta thinks resemble a group you already know, such as your best customers. You give Meta a seed, pick a country and a size, and it builds the new audience. Meta’s documentation sets minimum seed sizes and a clear size scale.
Updated 6 October 2026
An ad audience of new people who resemble a seed group you supply, such as customers. Meta builds it for one country, from the top 1% to 20% most similar.
Seeds and how they work
Meta’s guide says Lookalike audiences take sets of people as “seeds”, and Facebook builds an audience of similar people. It lists three kinds of seed: existing Custom Audiences, campaign or ad set conversions, and Page fans. You can use them for any objective, from fan growth to website sign-ups and purchases.
- From a Custom Audience: the seed must have at least 100 people.
- From campaign or ad set conversions: you need at least 100 unique conversions, and Meta recommends 200 or more. It uses up to 180 days of past conversion data.
- In every case you choose a country, and Meta finds the audience there. If too few seed members live in that country, there is an option to let it look for the minimum in another.
Choosing the size
The audience size is a percentage of the people in the chosen country, ranked by similarity. The guide describes two presets and a manual ratio.
| Setting | What it means |
|---|---|
| Similarity | The top 1% most similar people in the country: smaller, more precise |
| Greater reach | The top 5%: bigger, with a less precise match |
| Manual ratio | Any value from 1% to 20%, in steps of 1% |
A lookalike can take 1 to 6 hours to fully populate. The guide says you can create ad sets for it meanwhile, and delivery catches up when the audience is ready. If the lookalike belongs to an ad set, Facebook refreshes its members every 3 days.
Practical advice
- Seed quality beats quantity. A list of 200 paying customers says more than 5,000 people who clicked once.
- Start with the 1% audience, then widen it if delivery is thin.
- The 2025 restrictions on audiences that suggest health or financial status apply to lookalikes too, according to Meta’s notice on the same page.
Tip: Keep the seed and the goal aligned. A lookalike of people who bought is for sales. A lookalike of people who only followed will find more people who only follow.
An example
A skincare brand takes a Custom Audience of 800 repeat buyers, builds a 1% lookalike for its home country, and runs a launch ad to it. Anyone already on the buyer list is excluded.
Questions people ask
What is a Lookalike Audience?
A group of people Meta finds who resemble a seed audience you supply, such as customers, converters or Page fans. You pick a country and a size from 1% to 20% of that country’s people, ranked by similarity.
How many people do I need to create a lookalike?
Meta’s guide says a seed Custom Audience needs at least 100 members. For a lookalike from campaign or ad set conversions you need at least 100 unique conversions, and it recommends 200 or more.
What is the difference between 1% and 5% lookalikes?
Meta describes the 1% option as the most similar people, with a smaller reach and more precise match. The 5% option has greater reach but a less precise match. You can also set any percentage from 1% to 20%.
How long does a lookalike audience take to build?
The guide says 1 to 6 hours. You can create and run ad sets targeting it while it populates, and delivery catches up afterwards. The guide adds that members refresh every 3 days when it belongs to an ad set.
Sources
Related terms
- Custom AudienceAn ad audience built from people you already know, such as customers or visitors, which Meta matches to its users from data you supply, or from events you share.
- Meta PixelA snippet of JavaScript on your website that reports visitor actions to Meta, so you can measure ads, define custom audiences and analyse conversion funnels.
- Conversions APIA Meta connection that sends your website, app, messaging or offline events from your server or CRM to Meta, to measure outcomes and improve ad targeting.
- Lead adsFacebook ads with a built-in form, so people can sign up without leaving the app. The contact details they submit are stored against your Facebook Page.
- Cost per leadThe average you spend to collect one lead, such as a sign-up or an email address. Work it out as total spend divided by the number of leads.
- ROASReturn on ad spend: revenue attributed to your ads divided by what you spent on them. A ROAS of 3 means three units of sales for every one unit of ad spend.
More terms
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