
Harness the power of your
first-party data
What is First-id?
First-id enables you to identify all your consented users across every website, device, and browser, and recognize them within partner networks as well as offline. It delivers up to 60% more reach, while remaining fully GDPR-compliant, omnichannel, and independent with no login required and no encryption needed for sharing.


The cornerstone of your identification strategy
- Persistent, anonymous, and deterministic identification
- Omnichannel reach
- Controlled exposure frequency
- Deduplicated measurement
Advertisers
- Unify and enrich my 1st party data
- To identify, qualify and precisely personalize my interactions with users
- No email
Publishers / Media
- Unify and enrich my 1st party data
- To increase the volume and value of my audiences tenfold
- No email or third-party cookies
Agencies
- Optimize targeting and audience planning
- To increase the reach and impact of my media campaigns
- No third-party cookies
Adtech
- Maximize the interoperability of my tools
- For more precise, personalized and efficient service
- In compliance with RGPD

Whether you are a
media, e-retailer or advertiser
First-id helps you meet your challenges:
Data
- Identify
- Reconciling
- Qualify
- Exchange
Activation
- Target (Re-targeting)
- Address (Reach)
- Mastering repetition (capping frequency)
- Measuring performance
How does First-id help you respond to these challenges?
Deterministic
Precise, persistent identifiers based on a combination of strong signals
Powerful
Cross-domain, cross-device, cross-browser compatible
Interoperable
For use in all your marketing and advertising tools
Partner Sovereignty
The partner controls the creation and transfer of its first-party cookie
GDPR Compliance
User consent, opt-out management and anonymous ID
- Read more
+ 250 partner media sites and advertisers
Latest News
First-id, Klox and Rock en Seine: +52% ROAS Thanks to Our Meta CAPI Solution
Paris, September 23, 2025 – First-id is proud to announce a strategic partnership with Klox, the entertainment-focused media agency, and…
First-id and Decentriq: From Data Collaboration to Media Activation
In a context where data collaboration becomes a cornerstone of responsible advertising, First-id and Decentriq are taking a new strategic…
Google’s AI Overviews: 6 levers to remain visible and effective thanks to first-party data
On May 20, 2025, Google made a major strategic shift official: its search engine is becoming an answer engine, boosted…
Third-Party Cookies: The Great Comeback (or Not)? Why First-Party Data Remains More Essential Than Ever
Five years of announcements, U-turns, promises, and prototypes... only to end up back at square one. That’s how many in…