You are viewing the Legacy Marketing Campaigns API reference. For guidance migrating to the current version of Marketing Campaigns, see Migrating from Legacy Marketing Campaigns
For the most up-to-date information on the Custom Fields API, please visit the new Marketing Campaigns Custom Fields API.
The Custom Fields API lets you create and manage custom fields for your contacts. Custom fields are used to store additional information about your contacts. For example, you might use custom fields to store a contact's birthday, their favorite color, or any other information that is relevant to your business.