iOS 14 hid 55% of purchases — eight months stuck at 0.9x, then 2.8x

The situation

A Dutch electronics accessories brand selling in the Netherlands, Belgium, and Germany had been struggling with Meta performance since iOS 14. Their ROAS had been 2.6x pre-iOS 14. By mid-2023 it had declined to 0.9x and hadn't improved despite multiple creative refreshes and audience changes.

The problem

The brand was running Meta pixel only — no CAPI. Their European audience was predominantly iOS users with strict privacy settings. ATT opt-out rate in Western Europe is higher than the global average (~75%). 55% of their purchase events were invisible to Meta. The algorithm was bidding on a biased 45% sample of actual buyers.

What we did

1. Implemented Meta Conversions API via GTM Server-Side container hosted on Google Cloud
2. Passed all available customer data: hashed email, hashed phone, IP, user agent, fbc/fbp cookies
3. Implemented Consent Mode V2 to ensure compliance with Dutch/German GDPR while maximizing signal for users who consent
4. Set up a 30-day A/B test between old pixel-only campaigns and new CAPI-enabled campaigns to validate lift

Why it worked

The Western European market has the highest ATT opt-out rate globally — brands marketing there without CAPI are operating at the most severe disadvantage. Server-side CAPI is the only way to recover iOS signal in this market. The brand had spent 8 months changing creative and audiences when the real problem was data infrastructure.