Create a custom audience
Every great Meta campaign starts with an audience Meta did not have to guess at. A custom audience is built from your own data, customer lists you upload or behavior Meta already observed (website visits via Pixel, app activity, video views, Instagram or Facebook engagement, lead-form opens, offline events). It is the engine of retargeting and the seed every lookalike grows from, so master it before you touch interests.
Source types
Customer list (hashed upload), Website (Pixel and Conversions API), App activity, Offline activity, Video, Instagram account, Facebook Page, Lead forms, Events, Instant Experiences, Shopping, Catalog.
Customer lists must be hashed SHA-256 before upload. Meta hashes automatically if uploaded through the UI. Up to 15 identifiers per record are accepted: email, phone, name, date of birth, address, mobile advertising ID, and more.
Size and match rate
Minimum size to deliver ads: 100 people from the same country. Audiences under 1,000 frequently trigger an 'audience too small' delivery warning even though 100 is the technical floor.
Customer-list match rates typically land between 30 and 70 percent. Email matches better than phone because most users register with email.
Match rate decays roughly 10 to 20 percent every six months as emails and phone numbers go stale. Refresh customer lists quarterly.
Retention windows
Website custom audiences retain up to 180 days of activity. Page and Instagram engagement audiences retain up to 365 days. Lead-form audiences retain up to 90 days with sub-options for opened, opened-but-not-submitted, and submitted.
Video viewer audiences segment by watch depth: 3 seconds, 10 seconds, 25, 50, 75, or 95 percent of the video.
Restrictions
Special Ad Categories (housing, employment, credit, social issues) block most custom-audience targeting and disable lookalike creation from those audiences.
Beginning September 2025, Meta restricts custom audiences and lookalikes whose source data implies sensitive attributes like health conditions or financial status.
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