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

# User Properties

> Manage user-level attributes for segmentation and analytics

**User Properties** are key-value pairs attached to a user. They are used for segmentation, analytics filtering, and powering third-party integrations (e.g., sending user emails to Mailchimp or attribution IDs to AppsFlyer).

## Defined vs Custom properties

* **Defined properties** — Qonversion-reserved keys prefixed with `_q_` (e.g., `_q_email`, `_q_appsflyer_user_id`). These power built-in integrations.
* **Custom properties** — Any key you define for your own segmentation needs.

See the full list of defined properties in the [User Properties guide](/docs/user-properties).

## User Property object

| Field   | Type   | Description                                        |
| ------- | ------ | -------------------------------------------------- |
| `key`   | string | Property identifier. Defined keys start with `_q_` |
| `value` | string | Property value                                     |

## Available endpoints

| Method | Endpoint                 | Description                          |
| ------ | ------------------------ | ------------------------------------ |
| GET    | `/users/{id}/properties` | Retrieve all properties for a user   |
| POST   | `/users/{id}/properties` | Set one or more properties on a user |

## Authentication

All User Properties endpoints require a **Project Key** in the `Authorization` header.