> ## Documentation Index
> Fetch the complete documentation index at: https://docs.permutive.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Identity

> A foundation for accurate audience reporting and connecting auxiliary data

A user on a device is automatically allocated a unique device ID by the Permutive SDK on behalf of the publisher. This **user ID** is distinct across publishers, such that the same user who visits two different publishers' sites on their device will be assigned distinct IDs. As a first-party identity, it does not track users across domains or devices, and it has no reliance on third-party identifiers like cookies or mobile device IDs. The user ID is used in Permutive's cloud to generate accurate publisher-level audience insights, and on-device to store cohort information across sessions.

## Identifiers

In addition to the automatically assigned user ID, publishers can associate users with other **identifiers**. An identifier represents a specific ID type (such as an email address or a third-party identity) and consists of:

* **Tag**: The type of identifier (e.g., `email`, `uid2`, `rampid`)
* **Value**: The actual ID value for the user

Identifiers can be used to:

* **Unify cross-device behavior**: Connect a user's activity across multiple devices they are logged in to, enabling segmentation based on their combined behavior across sites owned by the publisher.
* **Connect auxiliary data**: Augment user segmentation with third-party audience data provided by partners (with appropriate user consent).
* **Enable identity-based activation**: Activate audiences through server-to-server integrations with partners that support identifier-based targeting.

Publishers can configure which identifier types they collect and use within their Permutive workspace through the Identity Graph.

## User group identifiers

In addition to user-level identifiers, Permutive supports **user group identifiers** that represent a group of users rather than an individual. The most common example is a **household ID**.

A household ID represents users residing in the same household, enabling publishers to:

* **Segment at the household level**: Build cohorts based on the combined behavior of all users in a household, such as "households with 5+ video starts in the last 14 days."
* **Target across devices**: Reach all devices in a household based on behavior observed on any member device—particularly valuable in CTV environments where multiple devices share a household context.
* **Apply household-level frequency caps**: Control ad exposure across all devices in a household rather than per-device.

Household ID graphs can be imported into Permutive via Connectivity from data warehouses such as BigQuery, Snowflake, or S3, and are managed through the Identity Graph alongside user-level identifiers.

## Identity resolution

**Identity resolution** is the process of linking multiple identifiers to the same user, creating a unified view across different touchpoints. When an identifier is set via the SDK or API, Permutive checks whether that identifier is already associated with an existing user. If a match is found, the user profiles are merged so that all identifiers resolve to the same Permutive ID. When multiple identifiers are provided, they are resolved in **priority order** (lower number = higher priority), allowing publishers to control which identifiers take precedence.

Enabling an identifier for resolution improves audience accuracy and cross-device reach, but it is important to consider the privacy implications for each identifier type. For guidance on evaluating these trade-offs, see [Understanding ID Resolution Privacy Considerations](/guides/signals/identity/understanding-id-resolution-privacy).

## Identity Graph

The **Identity Graph** is Permutive's core identity management system that collects, stores, and links identifiers to build a unified view of users across domains, devices, and sessions. It supports both user-level and user group-level identifiers, enabling publishers to build identity relationships for audience targeting, insights, measurement, and activation. Publishers configure their identifier types and manage the Identity Graph through the Permutive dashboard.