Paris, September 23, 2025 – First-id is proud to announce a strategic partnership with Klox, the entertainment-focused media agency, and Rock en Seine, one of Europe’s leading music festivals.
Faced with a structural challenge for all advertisers – the decline in performance caused by the disappearance of third-party cookies – we joined forces to deploy an innovative and future-proof solution.
The goal: to reconcile advertising performance, reliable measurement, and respect for data privacy.
As part of the 2025 Rock en Seine ticketing campaign, Klox orchestrated an A/B testing strategy on Meta. One audience was targeted using traditional methods (third-party cookies), while the other was fully activated through First-id’s deterministic identification technology, seamlessly connected to Meta’s Conversion API (CAPI).
The results clearly highlight the power of this approach:
- ROAS (Return on Ad Spend): +52%
- CPA (Cost per Acquisition): -22%
- Average basket value: +19%
- Meta Quality Score: +1.2 points
This collaboration demonstrates that first-party data, privacy-compliant and free of PII, can be transformed into an outstanding growth driver. It gives advertisers back full control over their reach and measurement—particularly in complex environments like Safari and iOS.
To explore the full details of this campaign, including analyses and insights from Klox, Rock en Seine, and First-id, download the complete press release below.