---
title: Devices
description: A device is a stable identifier for a physical phone, tablet, or computer. Multiple fingerprints can map to one device (same Mac, two browsers), and Rupt tracks them as a single entity for sharing and ATO checks.
---

# Devices

A device is a stable identifier for a physical phone, tablet, or computer in Rupt's data model. It sits one level above a [fingerprint](/docs/v3/concepts/fingerprints): multiple browsers on the same laptop produce different fingerprints but the same device. That's important for [account sharing](/docs/v3/concepts/account-sharing): an account with twelve fingerprints across two devices reads very differently from an account with twelve fingerprints across twelve devices.

## How devices are identified

The mechanism depends on how the SDK is shipped:

- **Native iOS**: uses the Identifier for Vendor (IDFV). Stable across reinstalls of the _same_ vendor's apps on the device, resets if every app from the vendor is uninstalled. Apple's anti-fingerprinting policy forbids more durable cross-app identifiers.
- **Native Android**: uses platform-provided device identifiers per Google's guidelines.
- **Web**: derived from the [fingerprint](/docs/v3/concepts/fingerprints) plus persistent storage hints. Not as stable as a native device ID; treat web devices as best-effort.

## What devices feed

Device counts are core to [account-sharing](/docs/v3/concepts/account-sharing) detection:

- `device_count`: devices currently attached to the user.
- `computer_device_count`, `tablet_device_count`, `mobile_device_count`: broken out by type, since the thresholds for "too many" differ (one phone is fine, six laptops is suspicious).

These are exposed as [checks](/docs/v3/concepts/checks) so [policies](/docs/v3/concepts/policies) can match on them directly.

## Devices vs fingerprints vs users

Rupt deliberately tracks all three layers:

- **[Fingerprint](/docs/v3/concepts/fingerprints)**: narrowest. A specific browser instance.
- **Device**: broader. The physical hardware behind one or more fingerprints.
- **User**: your account-level identity, independent of hardware.

A single user may legitimately span multiple devices (laptop, phone, tablet). A single device may legitimately host multiple fingerprints (Chrome, Safari, work browser, personal browser). What's _not_ legitimate is a single user with implausibly many devices. That's the sharing signal Rupt is built to catch, and the basis for the [people](/docs/v3/concepts/people) estimate.