Anonymised UserSync

What is UserSync

UserSync is our mechanism for allowing trusted third parties, such as CRM platforms, CDPs, login systems and other customer identity tools; to synchronise their own user identifiers with Anonymised’s on-device identity. This creates a privacy-safe bridge between an advertiser or technology partner’s first-party data and the anonymous cohort signals that Anonymised generates on the publisher side.

Why UserSync exists

Advertisers and CRM-based platforms often hold valuable membership lists based on transactions, loyalty, subscriptions or behavioural signals. Traditionally, activating those users on the open web has required cross-site tracking or server-side ID sharing. Both approaches introduce privacy, compliance and interoperability issues.

UserSync removes that barrier by allowing a partner to match their user ID to the Anonymised on-device identifier without ever sending us any personally identifiable information. Everything happens locally in the browser, with only cohort-level signals ever leaving the device. This keeps activation compliant while preserving the deterministic nature of our user recognition.

How UserSync works at a high level

UserSync follows a simple pattern:

1. Partner provides their user ID

   The partner’s website or tag sends their internal user ID to our JavaScript tag.

2. Local on-device mapping

   Our script stores a secure mapping between the partner user ID and the Anonymised ID in local storage.

3. Segment construction

   The partner can supply membership lists or rules using their own IDs. These are translated to Anonymised cohorts.

4. Activation across monetisation routes

   Once a segment is created, it becomes targetable across all pathways Anonymised enables, including:

   • SSP activation via header bidding routes and PMP deals

   • GAM via custom key-value targeting

   • Closed Loop Supply Optimisation

   • Any publisher integration that supports Anonymised cohorts

What this enables

With UserSync, partners can:

• Build deterministic addressable segments from their own first-party audiences.

• Target those audiences across our publisher network without exposing PII.

• Control frequency and measure performance through the Anonymised’s platform.

• Use their own ID space as the source of truth, which keeps operational workflows simple.

Outcomes for Publishers and Advertisers

Publishers gain higher-value demand from advertisers who can confidently target known audiences without requiring cookies or server-side ID sharing.

Advertisers/partners get a privacy-preserving way to activate real customer lists on premium inventory accessed through Anonymised.

Summary

UserSync creates a clean, compliant, future-proof identity handshake between third-party platforms and Anonymised’s anonymous ecosystem. It enables richer audience activation, more valuable PMPs and more predictable performance for both publishers and advertisers.

More information

From here, partners can explore:

• Integration guidelines — how to implement UserSync on your sites.

• API reference — endpoints, payloads, and authentication for segment construction.

• Best practices — consent handling, token management, and privacy compliance [coming soon].

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