Why attribution broke

Ad attribution in 2026 is less accurate than it was in 2020. iOS 14, cookie deprecation, and privacy regulation broke the old model. Advertisers who didn't adapt are operating blind. Those who did have new tools and frameworks.

What broke

iOS 14.5 (2021)

App Tracking Transparency gave users a choice to opt out of tracking. Most chose opt out. Pixel data from iOS users became incomplete.

Third-party cookies (phased out)

Chrome finally deprecated third-party cookies in 2024-2025. Cross-site tracking that powered retargeting died.

Privacy regulation

GDPR, CCPA, and successor laws make tracking more restricted and disclosure-heavy.

Safari and Firefox

Always ahead of Chrome on privacy. Strict third-party cookie blocking for years.

The consequences

The adaptations

Server-side tracking (CAPI)

Send events server-to-server instead of relying on pixel. Meta CAPI, Google Enhanced Conversions.

First-party data

Build and use your own data (email lists, CRM, user behavior on your site) rather than third-party tracking.

Blended metrics

MER, ROAS overall, not per-channel. Accept that platform-specific numbers are directional.

Incrementality testing

Holdout tests, turn a channel off and measure revenue change. Truer than platform reports.

Marketing Mix Modeling

Statistical modeling of total spend vs total revenue. Doesn't need user-level tracking.

What it means for day-to-day