Subscriber Key in Marketing Cloud Engagement

A subscriber key is a text field that contains a value that uniquely identifies a subscriber in Marketing Cloud Engagement. A subscriber key is limited to 254 English characters. Avoid using email addresses as subscriber keys.

When you use a subscriber key, the system uses this value to determine:

Whether a subscriber you import or create exists in the system.
Whether a subscriber appears multiple times on a list, group, or data extension to be sent a message. The subscriber key allows an email address to be included multiple times related to different subscriber key values.
Which subscriber record to update when a subscriber accesses their profile center or subscription center.
Which subscriber record to unsubscribe when a subscriber clicks the unsubscribe link in an email.

A subscriber key gives you the ability to identify subscribers with a value that you choose and have an email address appear multiple times related to different subscriber keys. Use a subscriber key to:

Maintain multiple sets of subscriber attributes for a single email address. For example, if a family shares an email address, you can use a subscriber key to uniquely identify each member of the family.
Include a single email address multiple times on a list. For example, send a separate message for each car a subscriber owns in a single send.

The Web Service SOAP API support functionality around subscribers identified with a subscriber key.

Note Though the subscriber key is the unique identifier, you must also provide an email address for each subscriber. Spam complaints are still tied to the email address.

For example, you could identify subscribers by an ID created by an external business system.

Note A subscriber key can contain different kinds of identifying information. Different subscribers with different kinds of keys could have the same information by coincidence. For example, if you import a subscriber keyed on phone number 3175551234 and a different subscriber keyed on external business system identifier 3175551234, the Marketing Cloud Engagement system interprets the subscriber key as the same subscriber.

Subscriber Key and Data Obscurity

When you use the data obscurity feature to protect your subscribers' personally identifiable data, the subscriber key is the only field in your data extension that isn’t encrypted.

Searching for Subscribers

You can perform a subscriber search based on the subscriber key value, email address, domain, status, and HTML email preference.

Exporting Subscribers

You can identify the subscribers to export using the subscriber key value. Regardless of the search criteria you use, the subscriber key value appears in the output file when you export subscribers.

Exporting Tracking Data

Exported tracking data is based on the subscriber key value. You can then import the tracking data into another business system and connect the tracking data with the subscribers as you identify them in that system. For example, you can use the identifier from your CRM system as the subscriber key. When you import the tracking data to your CRM system, the data is already connected to your contacts via the contact identifier.

The All Subscribers list shows only the most recent email address for each subscriber key. For example, you send an email to subscriber key “subkey1” using email1@domainA.com. Then later, you send an email to the same subscriber key using email2@domainB.com. The All Subscribers list shows only email2@domainB.com.

Subscriber key values can’t contain these characters.

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!
@
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$
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*
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Subscriber Key Scenario in Marketing Cloud Engagement
Review a scenario on using a subscriber key in Email Studio.
Identify Unique Subscribers Using Keys in Marketing Cloud Engagement
Identify unique subscribers by a value that isn’t an email address by enabling subscriber keys. Changing your implementation to use subscriber keys takes careful planning to avoid losing data during the process. To learn the best way to prepare and migrate your data, work with your account executive.