Facebook Lookalike Audiences are an excellent way to reach people who are similar to your existing customers and followers. When creating a Facebook Lookalike Audience, you can choose between a range of 1%-10% of the total population in your chosen target country, with 1% being those who most closely match your source
Because while a custom audience is built with your existing prospects, lookalike audiences let you explore and reach entirely new people who haven’t heard of your business ever before, but at the same time, they are very similar to your buyer personas and your current customer base.
To create a lookalike, your custom audience needs to have at least 100 people. If you don’t have enough people for a custom audience based on a product page, you could always create a custom audience that includes visits to all product pages or all pages on your website.
Context
When you create a Lookalike Audience, you choose a source audience (a Custom Audience created with information pulled from your pixel, mobile app, or fans of your Page). Facebook will identify the common qualities of the people in it (for example, demographic information or interests). Then, deliver your ad to an audience of people who are similar to (or “look like”) them.
You can choose the size of a Lookalike Audience during the creation process. Smaller audiences more closely match your source audience. Creating a larger audience increases your potential reach, but reduces the level of similarity between the Lookalike Audience and source audience. For example, if a source audience is made up of your best customers rather than all your customers, that could lead to better results.