Common mistakes with Custom Audience Exclusions in Meta Ads (especially Andromeda One setups) undermine signal quality and waste budget. Here's what trips up most advertisers.
Over-Excluding Audiences
Stacking 3+ exclusions (e.g., purchasers + email list + cart abandoners) shrinks reach below viable scale, leaving Andromeda starved for the 50 weekly events needed for optimization. Limit to 1-2 key exclusions like recent buyers (7-30 days) only.
Excluding in Wrong Campaigns
Applying prospecting exclusions (past purchasers) to retargeting ad sets defeats the purpose—your high-intent abandoners never see recovery ads. Use exclusions strictly in broad TOFU ad sets; pure remarketing gets zero exclusions.
Stale or Incomplete Custom Audiences
Forgetting to refresh "Purchases last 30 days" weekly via CAPI means yesterday's buyers stay excluded forever, while new converters slip through. Always sync pixel/CAPI events daily; test audience sizes (>1,000) before applying.
Forgetting Advantage+ Behavior
In ASC or broad setups, exclusions become "soft suggestions"—Andromeda may still serve 5-10% edge cases. Double-check Delivery Insights post-launch; tighten with narrower time windows (7d vs 30d) if leakage appears.
Set it once, audit weekly, and scale cleanly. This keeps your single ad set laser-focused on new converters.