Does the json import endpoint update an existing contact's list values?

[DanielH547]

Let's say I'm sending Contact A to both lists 123 and 456 using JSON import. Contact A already exists in 123. Will the JSON import endpoint be enough to add it to 456 as well, or do I have to call Add Contact to Lists endpoint, in addition, for it to be added to 456?

[Courtney_E]

Hello DanielH547,

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Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.

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Both of V3's Bulk Import endpoints (JSON and CSV) work similarly to uploading a file via the Website UI, in that it will only add list memberships (rather than remove any), and will only update contact fields that are provided via the file based on the email address of the contact.

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If you were to add a contact via one of the Bulk Import endpoints to list C, but they were already on lists A and B, they would now be on lists A, B, and C.

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Import Contacts using a JSON Payload

(POST /activities/contacts_json_import)

https://developer.constantcontact.com/api_reference/index.html#!/Bulk_Activities/bulkImportContactsJ...

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Import Contacts using a CSV File

(POST /activities/contacts_file_import)

https://developer.constantcontact.com/api_reference/index.html#!/Bulk_Activities/contactsCSVImport

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Please have a look and let us know if you have any other questions!