What is Custom Audience?
An audience built from your own data — customer email list, website visitors, app users, video viewers — for targeting or exclusion.
The detailed definition
Custom audiences are the building block of retargeting and lookalike modeling. The most common types: customer file upload (email/phone hashed for matching), website visitors from your Pixel, app users from your SDK, and engagement audiences (people who watched your video, engaged with your post). Post-iOS 14.5, Pixel-based custom audiences shrunk meaningfully for paid social — the signal that built them is partially blocked. Server-side data sources (CAPI for Meta, Enhanced Conversions for Google) restore some of the missing signal. Customer file uploads remain useful for first-party retargeting where you have the email address.
Related terms
Frequently asked about Custom Audience
›What are the different types of custom audiences?
Five main types: customer file (email/phone hashed), website visitors (Pixel-based), app users (SDK-based), video engagement audiences (people who watched X% of a specific video), and offline events (CRM-uploaded conversion data). Each has different post-iOS reliability characteristics.
›Have custom audiences gotten worse since iOS 14.5?
Yes for browser/app-based audiences (Pixel and SDK-based shrunk 20–40% in many cases). No for first-party data audiences (customer file uploads, CRM data, server-side events via CAPI). The lesson: first-party data is the most durable acquisition signal.
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