Updated: Jan 7, 2020
The short answer is 100, but often requires more. This minimum requirement is meant to protect the privacy of the audience members, reducing the likelihood of identifying individuals via Facebook pixels or their actions on ads. There have been instances of Facebook denying use of audiences that were well over 100 but less than 1,000, so it’s always safe to shoot for a larger audience wherever possible. If you can’t reach 1,000, use the Audiences module, to see your list of audiences and their “Availability” for use in ad sets
While 100 is the minimum number of people in a custom audience who can be served your ad, it's important to recognize that any list you import should be much bigger than this for a variety of reasons that I touch on below.
Firstly, it’s important to understand how it works.
Most common data sources of custom audiences for Facebook Ads:
Website visitors - data collected by a Facebook Pixel
List of customer phone numbers
List of customer email addresses
Facebook then cross-references that imported information with their user database to match Facebook users to the data you import. The end result is a custom audience of Facebook users that can be served ads directly, and this audience must total at least 100 users. Ergo, some of the contacts in your initial list will not be linked to a Facebook account, so uploading 100 phone numbers alone will not be enough.
From Custom to Lookalike Audiences
An overabundance of data is also an advantage to the Facebook algorithm, which identifies those users most likely to act in accordance with your Campaign Objective. Their algorithm is then able to use your custom audience to create a Lookalike Audience of new customers with similar interests. The effectiveness of this Lookalike Audience depends solely on the amount of data it can use as a reference. For example, say you have a list of customers that have purchased your bird feeders. Facebook can use that list to identify potential customers who would also purchase bird feeders. Providing a large list of 5000 customers with varied interests & behaviors would result in a much more effective Lookalike Audience than one of only 100.
Tools Take the Pressure Off
AdRobin can speed up this process and boost the effectiveness of Lookalike Audiences by creating them with minimal effort on the part of its clients. You can stipulate exactly what you want your audience to look like, upload a custom list, or use our advanced auto-targeting system for hassle-free publishing.
At AdRobin, we help businesses and marketers streamline the process of creating and deploying online ads. Click here to learn more about how AdRobin can simplify your online advertising.