02 · Identifiers & First-id

Recognise your visitors durably, with or without cookies, always within consent.

Cookieless first-party identifier

Assigns each visitor an identifier specific to your site, without setting a cookie. It cannot be used to follow that person across other sites.

Technical detail

Domain-specific cookieless identifier (no cross-site tracking). Value unsubscribed if the service is inactive or the DPA is unsigned, objected if the user has objected to processing, otherwise a UUID v4.

Related header: Gtm-Helper-Cookieless-Id-Domain-Specific.

Cookieless third-party identifier

Generates a universal cookieless identifier, recognisable from one site to another. Useful for ad targeting and subject to consent.

Technical detail

Universal cookieless identifier (allows cross-site tracking). Value unsubscribed if the service is inactive or the DPA is unsigned, no-consent when consent is absent, otherwise a UUID v4.

Related header: Gtm-Helper-Cookieless-Id-Cross-Domain.

Automatic First-id support

Enables First-id, a first-party advertising identifier that improves campaign performance, only with the user's consent.

Technical detail

Immediate activation, implying automatic acceptance of the First-id DPA and terms of use. Compatible with every TCF-supporting CMP. Declare the First-id vendor (1178) to benefit fully.

Related header: Gtm-Helper-User-First-Id.

↳ Automatic redirect after consent

First-id sub-option

Reloads the page after consent. The experience is slightly impacted, but identifiers last longer, especially on Safari/iOS.

Technical detail

By default the First-id Flex offer is used (base version). This redirect extends the lifetime of generated identifiers, particularly in environments where third-party cookies are disabled (Safari/iOS).

Going further

• Integrating Sirdata data into the GTM layer

• GTM Helper layer — full header list

• First-party infrastructure & cookie optimization