Lookalike audiences allow advertisers to target more people who are similar to their established customers. A lookalike audience uses a given user set as a "seed," and an audience is built of similar users. Lookalike audiences can be used to support any business objective: targeting people who are similar to sets of customers for fan acquisition, site registration, off-Facebook purchases, and coupon claims, or simply to drive awareness of a brand.
You need to have at least one source based on which we will create your lookalike audience:
In the Audience section, in Custom Audiences, choose Create New > Lookalike Audience.
Pick the source from which we should create your lookalike audience: Facebook Page or Custom Audience. Next choose a country to further define your lookalike audience.
Once you pick a source and country, you can select the size range of your lookalike audience. Size range is based on the total audience in the country you choose:
Smaller audiences most closely match your source audience.
Creating a larger audience increases your potential reach, but reduces the level of similarity to your source audience.
After you create your lookalike audience configuration, we will run the compilation of your audience in a background process. It may take up to 2 hours for your audience to be ready. In the meantime, you can continue creating and booking your ad. Your ad will not be ready until the audience is ready. You can check its status in the Audiences tool in the Ads Manager.