Since Apple introduced App Tracking Transparency (ATT) in iOS 14.5, every iPhone user sees a pop-up asking whether to allow apps to track them across other apps and websites. Most surveys find only around 20–30% of users tap “Allow,” which means more than half of the conversion data the Facebook Pixel used to track through the browser has disappeared on iOS.
The real impact on advertising
When the Pixel can't see conversions from iOS users who opt out of tracking, Facebook's algorithm loses key data for finding audiences likely to buy. Cost per conversion (CPA) goes up, and Lookalike Audiences that used to be accurate start drifting, because the source data is smaller than reality.
What is the Conversion API (CAPI), and what does it fix?
The Conversion API sends conversion data directly from your business's server to Facebook, instead of relying solely on the browser-side Pixel. It bypasses browser restrictions and ad blockers and isn't directly affected by ATT opt-outs, because the data goes server-to-server. As a result, you keep a much more complete picture of your conversions.
How the Pixel and CAPI work together (deduplication)
Meta recommends always using the Pixel and CAPI together. The system automatically deduplicates using an Event ID so the same conversion isn't counted twice from two sources. The more high-quality data you send through CAPI, such as hashed emails or phone numbers, the more accurate Facebook's matching becomes.
First-party data is your most valuable asset today
Beyond CAPI, businesses should start building their own first-party data, such as customer records from a CRM, LINE OA members or purchase history, to create Custom Audiences and Lookalikes that don't depend on third-party cookies, which are being restricted more and more on every platform.
- Check whether your business has installed the Conversion API alongside the Pixel
- Use the Event Match Quality score in Events Manager to measure the quality of the data you send
- Keep collecting first-party data through your CRM or LINE OA
- Don't stop an ad channel based only on falling conversion numbers. Check actual sales in your store system too.
Summary
The impact of ATT doesn't mean advertising on iOS no longer works. It means businesses need to invest more in their own data infrastructure. The Markettung team sets up the Conversion API and first-party data systems for every client who starts advertising with us, so the data behind every decision is as accurate as possible.