Our v3 API is now available! Learn more by visiting the v3 developer portal. Creating new v2 API keys is no longer supported.

API and GUI Differences

Unsupported GUI functionality

The Constant Contact v2 API does not currently support certain functionality available when logged into an account. These new features are very different from previous product functionality, and we are not able to support them while maintaining consistent, predictable API behavior. We've captured unsupported functionality below.

Birthday and Anniversary fields

Birthday and anniversary fields are not supported through the full API.

Physical addresses

Although our UI accepts multiple HOME, PERSONAL, VACATION, and OTHER physical addresses, The API can only create, modify, and retrieve 1 BUSINESS address and 1 PERSONAL address. 

state_code field - the state_code field does not display when viewing a contact record in the Constant Contact product UI. The field is retained as part of the contact object, and can be written to and viewed using the API.

Custom fields

Naming Convention - The contact API endpoints currently only support the CustomFieldn naming format, where n= 1 - 15. The new contact management system allows custom fields with very few naming restrictions. The API ignores custom fields not using the format CustomFieldn. These will be viewed as "Custom Field n" through the UI.

Display Order - The API does not display Custom Fields in response payloads in any particular order. If custom fields are imported as part of the contact record, the order in which they are imported has no bearing on how they are displayed either in the UI settings section (where you manage custom fields) or in the individual contact record. 


The UI supports multiple notes for a contact, but the API supports a single note for a contact and ignores additional notes. 


Tags are a feature available in the UI that provide a way to group contacts together for targeted emails or just as a way to organize your contacts. The v2 API does not currently support tags with contacts.