Lookalike and Custom Audience: The differences

Lookalike and Custom Audience: The differences

26 February 2023 |

Data, Insights, Privacy

The most successful social media campaigns are based on identifying and targeting the correct audiences, by utilising as many signals as possible. Two effective audience selection tools available on Facebook are custom audiences and lookalike audiences. Lookalike audiences are also called Similar Audiences within Google, for the purpose of this article we are talking about the same targeting option. Let’s explore the differences between them.

Custom Audiences

Custom audiences comprise data sets of people who have interacted with your business through various channels in some way, including:

  • Visiting your website
  • Engaging with your Facebook/Instagram page
  • Watching your videos
  • Using your app
  • Attending events
  • Submitting a lead form
  • Engaging in offline activities
  • Being listed in your customer file

You can use custom audiences to send special offers or promotions to your existing customers, nurture existing leads, provide more in-depth information to those who have engaged with your content, or remind people who have shown interest but haven’t made a purchase yet. In essence, custom audiences are an excellent tool for retargeting and reminding. Yet they can also be used as an awareness tool or cross-selling to other products or services you offer.

Lookalike Audiences

Lookalike, or Similar, audiences are composed of people who share similar characteristics with your source audience. For instance, if you create a lookalike audience based on your Facebook page likes, Facebook will identify users who have similar interests and behaviours to those who like your page.

Lookalike audiences can be classified as cold audiences because they haven’t interacted with your business before. However, they offer a robust audience targeting option that enables you to expand your campaign’s reach to new audiences who are likely to engage with your content or offer.¬†

Lookalike audiences are a powerful tool as they utilise more data points than advertisers humanly can, and are a much more effective way of automating the process of defining your target audience. Similarly, there may be characteristics that you are not aware of from your own data set but that Facebook or Google can identify for you.


When using lookalikes the audience size should be considered. Facebook for example has a minimum of 100 users to be able to be used in the platform, whereas Google requires 1,000 users minimum to utilise the custom audience and lookalike features. Ensuring your chosen data set is big enough is the first step.

Consider next the recency and segmentation of your chosen data set. How old is the data? How have you segmented the data in order to best inform the lookalike model to find new customers? Giving conflicting signals by combining data sets is going to be misleading for the algorithms to find new audiences, and your campaigns may not be as effective.

Custom and lookalike audiences serve different purposes, and each has its advantages. At Admatic, we have a wealth of insights to share with you. Be sure to stay tuned and follow us for more information.