How to Pick a Lookalike Source Audience

Advertiser method. Meta does not publish this as a rule. The mechanics below come from Meta’s documentation; the method itself is common advertiser practice, and results vary.

Pick a source when you want Meta to find new people who resemble a group you already have and you can say which group that is. It fits poorly when you have no group of at least 100 people, because Meta needs that much to start. In short, the source is the audience Meta copies traits from, so you are choosing which of your people you want more of.

What can be a source?

Meta defines a source audience as the audience a lookalike is based on. Its example is a Page: if you build a lookalike from your Page fans, the fans are the source. Meta’s create page lists the permission needed to build a lookalike from a custom audience, a Page, the Meta Pixel or an app, and each source has its own.

Two things cannot be a source. Meta says saved audiences can’t be used, and an exclusion-only customer list can’t be used to make a lookalike. If you might want a customer list as a source, don’t choose exclusion-only when you upload it.

How big does the source need to be?

Meta says you need a source with at least 100 people and generally recommends between 1,000 and 5,000. Meta says a status of “audience not created” might mean the source was too small. You can create up to 500 lookalikes from one source, and people in the source are excluded from the lookalike.

Should the source be all customers or a narrower group?

The Meta pages cited here do not say which group to pick. They say the quality of the source matters, and that you may get better results, depending on your goals, from an audience made from your top customers than from one that includes all of them. A regular lookalike, Meta adds, can only find people similar to all your customers.

The trade-off is yours to weigh. A narrower group sits closer to the customers you value most, but it is smaller and still has to clear Meta’s minimum. A wider group is easier to size but includes people you may value less. Which one fits is your judgment, not a Meta rule.

If you track a value for each customer, Meta describes a value-based lookalike as one made of the people most similar to your highest-value customers. With a custom audience, that means adding a customer lifetime value column to the file you upload. Meta says you can also use a Meta Pixel, SDK, catalog or mobile app as the source.

How does the source relate to size and location?

They are separate choices. The percentage you pick sets how closely the new audience matches the source: Meta says smaller percentages match more closely and larger ones build a bigger, broader audience. Location comes later. Meta says you no longer select a location when you create a lookalike; it uses the ad set’s location settings to find people similar to the source.

What happens to the source once ads run?

Meta says Advantage+ lookalike uses the custom audience your lookalike was based on as a guide for delivery while it assesses performance. It may reach people beyond the percentage you chose when it sees better performance. Meta says this is on automatically for new, duplicated and draft campaigns and ad sets using lookalikes made from mobile, website or customer list custom audiences. On that description, the source stays the guide for delivery even when Meta expands past it. That is a reading of Meta’s wording, not a Meta statement.

How can you decide for your own account?

List the groups you hold that meet the 100-person minimum.
Pick the group you want more of, such as buyers, rather than everyone you have.
Check it isn’t a saved audience or an exclusion-only list.
Create the lookalike, then compare it with your current audience in your own reporting.

FAQ

Can I use a saved audience as a lookalike source?

No. Meta says saved audiences can’t be used as a source when you create a lookalike. Use a custom audience, a Page, the Meta Pixel or an app instead, and check you have the permission Meta lists for that source.

Will my source people be in the lookalike?

No. Meta says people in your source audience are excluded from your lookalike audience. So the lookalike does not contain the people in the source. Reaching the source people themselves takes the source audience, which you can include in an ad set as its own audience.

What if my source is too small?

Meta says a source needs at least 100 people and generally recommends 1,000 to 5,000. If the status reads “audience not created”, Meta says this might mean the source was too small, and you can try again.