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Facebook Custom Audience Reach Estimates Are Back: Just The Facts

July 11, 2019 Kathy Bryan

After a year-long hiatus, Facebook is in the process of reintroducing reach estimates for Facebook custom audience targeting. Because reach estimates allow Facebook advertisers to better plan and budget their campaigns, this is a welcome change across the digital marketing community.

What Are Facebook Custom Audience Reach Estimates?

facebook custom audiences

Facebook’s custom audience reach estimates allow advertisers to understand the size of a custom audience before launching a campaign. “In general, digital advertisers want their audiences to be as targeted as possible, often with campaigns targeting the Facebook user profiles that are most similar to the user profiles of people are already customers of a brand,” noted Jonathan Katz, Chief Media & Product Officer of Digital Media Solutions.TM “However, sometimes narrow targeting can make a campaign’s reach too small, meaning the ads will not reach enough Facebook users to make an impact. Plus, constricted targeting can increase top-of-funnel media costs. Facebook custom audience reach estimates allow advertisers to understand the size of the audience they are reaching so they can plan their campaigns and their advertising budgets properly.”

Why Did Facebook Suspend Custom Audience Reach Estimates In 2018?

In 2018, information about a bug related to Facebook custom audience reach targeting was submitted to the Facebook Bug Bounty. The bug allowed users uploading lists to “infer attributes by identifying rounding thresholds and adding users one by one until the audience estimate changed.” After reviewing the security concerns, Facebook responded by removing all potential reach numbers from custom audience campaigns on March 23, 2018.

Why Is Facebook Relaunching Custom Audience Reach Estimates?

Facebook Relaunching Custom Audience Reach

According to the Facebook Bug Bounty account on Facebook, “Since suspending this feature [custom audience reach estimates] last year, we’ve been working with researchers to improve the security of our custom audiences reach estimate feature. We focused on three key areas to curb potential misuse: privacy, protection and new usage restrictions. With these updates now in place, we are reinstating custom audience reach estimates. We continue to be grateful to the researchers who identified the bug and for working with us to fix it.”

Facebook custom audience reach estimates were re-introduced to the first set of advertisers on July 2. The rollout is randomized and is expected to continue throughout the year.

What Fixes Did Facebook Make To Their Custom Audience Reach Estimates?


Facebook’s revamped custom audience reach estimates tool incorporates three security-related fixes:

  1. The rounding logic for custom audience reach estimates is now more complex, making it harder for users to identify rounding triggers.
  2. An improved backend detection process has been implemented to help the Facebook business integrity team detect potential misuse.
  3. There are new restrictions on the number of API calls each individual account can make to the custom audiences reach estimator.

None of the changes implemented to Facebook’s custom audience reach estimator are expected to impact proper use of the tool for estimating audience sizes in conjunction with typical advertising campaign planning.

Do Facebook Users Know When Custom Audiences Are Used For Ad Targeting?

Yes, Facebook users are provided transparency to see data regarding custom audience targeting. In February, Facebook unveiled “Why am I seeing this?” information boxes that can show the name of the businesses that uploaded custom audience files plus additional information related to the files, including upload dates.

Will The Facebook Clear History Tool Impact Custom Audience Targeting?

Facebook already allows users to clear their histories of data collected within Facebook, and only a small percentage of users take this action. Later this year, Facebook is expected to let users also clear their histories of data collected by Facebook from events that occur outside the Facebook universe (within external apps and websites). When users clear history, it impacts an advertiser’s ability to target them. However, most predict the number of users clearing history will remain low enough to have minimal impact on ad targeting.

“The return of the Facebook custom audience reach estimate tool is a win for digital marketers,” according to Katz. “When ads are properly targeted and personalized, consumers are happy to be engaged by marketers. Facebook custom audiences allow for this tight targeting, and the reach estimates let advertisers understand which audiences are large enough to warrant the effort.”

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About the Author

Kathy Bryan

Kathy Bryan is the Chief Marketing Officer at Digital Media Solutions (DMS). In this role, Kathy is responsible for all aspects of marketing and communications for DMS, the leading global martech company leveraging innovative, performance-driven brand and marketplace solutions to connect consumers and advertisers.

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