---
schema_version: "1"
id: 27f35f0b28e976d137c313944a0e3ade3bffbc5fb689204a0608648efc209159
title: Set the Subscriber Key or Contact Key
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/mktg/264-0-0/mc_mp_use_case_subscriber_key.md
canonical_url: https://help.salesforce.com/s/articleView?id=mktg.mc_mp_use_case_subscriber_key.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 3653298d6aedf96311d207fafe51b71d0fac77fdc4c16cb8dffb3e09c6b8702f
description: Contact key, also known as subscriber key, is the unique identifier used to aggregate a contact’s devices in Marketing Cloud Engagement. Set the contact key to a specific value provided by your customer or to another unique identifier for the contact. You can use a mobile number, customer number, Salesforce ContactID, or another value.
products:
  - Marketing
  - Marketing Cloud Engagement
release: "264"
---
# Set the Subscriber Key or Contact Key

Contact key, also known as subscriber key, is the unique identifier used to aggregate a contact’s devices in Marketing Cloud Engagement. Set the contact key to a specific value provided by your customer or to another unique identifier for the contact. You can use a mobile number, customer number, Salesforce ContactID, or another value.

For specific details on how to set the contact key for Android and iOS apps, see [Register Contacts with Marketing Cloud Engagement](https://developer.salesforce.com/docs/marketing/mobilepush/guide/register-contacts-with-marketing-cloud.html).