Lookalike audience

• Quality over quantity: high-value customers often produce a better lookalike than all customers.
• Recency: people who bought recently reflect today's buyer better than a list from years ago.
• Size: Meta requires at least 100 people from one country in the source audience.
• Consent: only upload customer data you are permitted to use for advertising.

As delivery systems have improved, many advertisers find broad targeting performs as well as or better than lookalikes, because the algorithm finds responsive people from the creative itself. In that model, the ad becomes the targeting: who stops for it tells the system who to show it to next.

These people do not know you, so treat them as a cold audience. The ad needs to introduce the problem, the product and why it is different, which is a different brief from retargeting.

• Meta: you choose a percentage range; smaller percentages match the source more closely, larger ones make a bigger, broader audience. Meta notes a source of your best customers may work better than one of all customers.
• Meta's Marketing API requires at least 100 people from a country in the source audience, and sets lookalike size from 1% to 20% of that country.
• Meta limits or removes lookalike audiences for some ads about financial products and services, employment or housing. Check this before planning fintech, recruiting or real estate campaigns around them.