---
title: Identity Resolution — Customer Data Platforms Module 3 — RGM Training
url: https://realgrowthmatters.com/training/customer-data-platforms/identity-resolution/
updated: 2026-06-10
source_html: https://realgrowthmatters.com/training/customer-data-platforms/identity-resolution/
---

RGM° · Training

# Identity Resolution

Identity resolution links a user's many identifiers into a unified profile. This module covers deterministic vs probabilistic, the major identifiers, and the quality measurement that prevents bad personalization.

### What you will learn

1. Why identity resolution is the heart of a CDP
2. Deterministic vs probabilistic matching
3. Identity graphs and their construction
4. Common identifiers and their reliability
5. Cross-device matching
6. Cross-domain matching
7. Online-to-offline matching
8. Privacy considerations
9. Vendor identity solutions (LiveRamp, Tapad, etc.)
10. Measuring identity-resolution quality
11. Common identity-resolution mistakes

## 1. Why identity resolution

A user appears in dozens of systems with different identifiers: web cookies, mobile IDs, email, phone, customer-ID. Identity resolution links these into a unified persistent profile. Without it, every marketing system has a partial view of the customer.

## 2. Deterministic vs probabilistic

| Type | How it works | Accuracy |
| --- | --- | --- |
| Deterministic | Exact match on known identifier (email, phone, customer-ID) | Very high when match exists |
| Probabilistic | Statistical match on signals (IP, device, behavior) | Moderate; declining due to privacy |

## 3. Identity graphs

An identity graph stores relationships between identifiers. Each node is an identifier; each edge is a confidence-scored relationship. The graph grows as new signals connect previously-disjoint identifiers.

## 4. Common identifiers

- Email (highly reliable, persistent).
- Phone (highly reliable, persistent).
- Customer-ID (most reliable for known customers).
- Device IDs (mobile MAID; reliability declining).
- First-party cookies (browser-specific, expire).
- Third-party cookies (deprecated).
- Login session.
- IP address (low-quality identifier, especially with mobile).

## 5. Cross-device

Linking a user's desktop, mobile web, and mobile app. Methods: login (most reliable), email collection, deterministic match via shared identifier, probabilistic via behavior/location.

## 6. Cross-domain

Linking the same user across multiple owned domains. Methods: first-party cookie + login, server-side identity stitching, third-party graph (LiveRamp).

## 7. Online-to-offline

Linking online identifiers to offline customer records. Methods: email/phone capture, in-store login, transaction matching, third-party graph providers.

## 8. Privacy

- Identity work concentrates PII; treat with appropriate security.
- Consent requirements vary by jurisdiction.
- Right-to-deletion must propagate across the identity graph.
- Hashing PII for vendor sharing.

## 9. Vendor solutions

- **LiveRamp:** The leading commercial identity graph.
- **Tapad (Experian):** Probabilistic device graph.
- **Adobe Real-Time CDP:** Adobe-native graph.
- **Salesforce Data Cloud:** Salesforce-native graph.
- **Acxiom (IPG Mediabrands):** Marketing identity graph.
- **The Trade Desk Unified ID 2.0:** Email-based open identity.

## 10. Measuring quality

- Match rate: percentage of records that resolve to a known profile.
- Match accuracy: confirmed correct matches vs total.
- Profile completeness: data points per profile.
- Recency: how current the linked identifiers are.

## 11. Common mistakes

Treating one identifier as authoritative when conflicts arise. Not de-duplicating profiles after merge. Letting low-confidence probabilistic matches drive personalization. Not propagating deletion requests across the graph. Ignoring consent state in identity stitching.

**How to use this module:** The deterministic-vs-probabilistic table (Section 2), the identifier list (Section 4), and the quality metrics (Section 10) are the planning artifacts.

### Sources & further reading

- [LiveRamp blog](https://liveramp.com/blog/)
- [Experian Identity Resolution](https://www.experian.com/marketing-services/identity-resolution.html)
- [Unified ID 2.0](https://unifiedid.com/)
- [Acxiom insights](https://www.acxiom.com/insights/)
- [CDP Institute identity](https://www.cdpinstitute.org/insights/identity-resolution/)
- [Segment identity](https://segment.com/blog/identity-resolution/)
- [mParticle identity](https://www.mparticle.com/blog/identity-resolution/)
- Books: Martin Kihn & Chris O'Hara, *Customer Data Platforms*; Jed Williams, *Identity Crisis*
- [IAB Identity Resolution](https://www.iab.com/insights/identity-resolution/)
- [Tealium AudienceStream](https://www.tealium.com/products/audiencestream-cdp/)
- [Salesforce Identity Resolution](https://www.salesforce.com/products/data/identity-resolution/)
- [TTD UID2.0](https://thetradedesk.com/us/news/the-trade-desk-launches-unified-id-2-0-as-an-industry-effort)

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Part of the [Customer Data Platforms](/training/customer-data-platforms/) series · RGM Training