What is a Custom Audience?

A custom audience is an ad-account segment built from the advertiser’s own data—not only platform interests. Sources include website visitors (pixel), app users, email/phone lists, engagement (video, lead forms), and CRM buyers.

Uses

Retargeting — ads to visitors and abandoners.
Exclusions — suppress ads to users who already converted.
Lookalike seed — base for conversion lookalikes.
CRM upload — reactivation where policy allows.

Tracking connection

A landing pixel and tracker postbacks do not replace custom audiences in the ad account: the pixel builds platform audiences; the tracker records clicks and conversions for ROI. For precise exclusions, teams sometimes export converting sub_ids or send CAPI/server events from tracker/MMP.

Platform requirements

Hashed PII (SHA-256 email/phone), EU consent, minimum audience size before delivery (often 100–1,000). Data matching is imperfect—match rate affects reach.

Notes

Custom audiences decay over time (membership duration). Mixing GEOs in one list hurts targeting. Uploading third-party lists without consent violates policy and GDPR.