Custom Audience
Paid MediaAlso: custom audiences · matched audience · first-party audience
Quick definition
Ad targeting audiences built from your own first-party data — email lists, website visitors, app users or CRM records. Custom audiences let you show ads to people you already have a relationship with, or find new people who look like them.
Where it shows up in the data
Built from website activity tracked via a platform pixel. Website visitors, product viewers, cart abandoners, purchasers. The most common retargeting foundation.
Upload your email or phone number database, and the platform matches those records to its users. Match rates vary (40-70% typically). Meta is best at this; LinkedIn and Google are reasonable.
The platform finds users who statistically resemble your custom audience. A 1% lookalike in Australia finds the ~170K Meta users most similar to your seed audience. Lookalikes are weakening as privacy restrictions reduce signal quality.
Using custom audiences to exclude existing customers from acquisition campaigns. Prevents wasting acquisition budget on people who already bought.
What it actually means
Custom audiences let you translate your offline relationships into digital targeting. Your email subscribers, past customers and website visitors become targetable cohorts on Meta, Google, LinkedIn and TikTok. This is more valuable than platform-built interest audiences because you know something specific about these people — they've bought from you, subscribed to you, or expressed interest in a concrete way. Custom audiences are the bridge between your CRM and your paid media strategy.
Your CRM is an ad targeting asset. Most businesses treat it as just an email list.
How it shows up
Custom audiences appear in Meta Ads Manager, Google Ads, LinkedIn Campaign Manager and TikTok Ads Manager. You can see match rates, audience sizes and how campaigns perform against each audience segment. Monitor audience overlap between segments to avoid showing the same person the same ad from multiple campaigns.
The Australian context
Australian custom audiences are subject to Privacy Act requirements. Uploading customer data to ad platforms requires that customers consented to their data being used for marketing. Meta's EU data residency changes have affected some Australian business account setups. Ensure your terms of service and privacy policy cover data use for advertising purposes.
Where people get this wrong
Related terms
Common questions
How do I build a custom audience in Meta Ads?
In Meta Ads Manager, go to Audiences, select Create Audience and choose Custom Audience. You can upload a customer list (CSV with email, phone, name), connect your pixel for website-based audiences, or use your app data. Match rates are typically 40-65% for email lists.
Are custom audiences affected by iOS 14 privacy changes?
Pixel-based website visitor audiences have been significantly reduced by iOS 14's App Tracking Transparency framework. Email-matched custom audiences are less affected since they don't rely on device tracking. This is one of the primary reasons to invest in email list building — it creates targeting audiences that survive privacy changes.
Keep exploring
About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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