Bulk Upsert Contacts

Creates or updates multiple contacts in a single request. Works synchronously.

Each contact is matched against existing contacts using the contact matching logic. If a match is found, the contact is updated. Otherwise, a new contact is created.

When a contact is updated, upsertMode controls how:

• OVERWRITE (default): Replaces existing field values.
• APPEND: Sets a non-array field only if it doesn't already have a value, and appends to array fields.
• OVERWRITE_APPEND_ARRAYS: Overwrites non-array fields and appends to array fields.

In APPEND or OVERWRITE_APPEND_ARRAYS mode, the default address flag is ignored unless the contact has no existing addresses.

When you provide an image URL and the upsert mode allows the image to be updated, the image is uploaded in the background. The returned contact temporarily has no image if it was created, or its previous image if it was updated. Once the upload succeeds, the contact's image is updated.

To create or update a single contact, call Upsert Contact.