Meta Ads

What Is Custom Audience?

Q: How big should a Custom Audience be?

Minimum 1,000 users to serve. For retargeting, 5,000+ works well. For lookalike seeds, 2,000–50,000 hits Meta's sweet spot.

Q: How often do Custom Audiences refresh?

Pixel-based audiences refresh in near real time. Customer list uploads are static — re-upload monthly or automate via CAPI + CRM sync.

Q: Do Custom Audiences work across ad accounts?

Not directly. You'd need to share them via Business Manager permissions or re-upload the source list in the new account.

A Custom Audience is a Meta audience you build from your own first-party data — a customer list, Pixel events, video views, page engagement, or app activity. It's the foundation of retargeting, LTV-based prospecting, and exclusion targeting.

Common types

Upload your last-90-day purchaser list (hashed CSV) to build a purchaser audience. Create a Pixel-based audience of 'people who added to cart in last 14 days but didn't buy.' Build an engagement audience of 'anyone who watched 50% of your video ads in the last 30 days.' Combine these into layered retargeting funnels or as seeds for lookalikes.

Benchmarks

Minimum size to activate: 1,000 users.
Match rate on customer list uploads: 40–75% depending on data quality.
Retargeting CPMs are typically 2–4× cold prospecting CPMs.

Why it matters

Custom Audiences are your defensible advantage — competitors can't copy your customer list. They fuel retargeting, exclude existing customers from prospecting, and seed high-quality lookalikes.

Common mistakes

1.Not excluding existing customers from prospecting campaigns — wastes budget re-acquiring.
2.Using a small (< 500) seed for lookalikes — Meta can't find pattern.
3.Uploading unhashed data. Meta requires hashing; unhashed uploads get rejected or drop match rate.