Update a contact property

PATCH/v1/contact-properties/{id}

Change the fallback value. The key and type cannot change.

Required scope: contacts:manage

Parameters

Name	In	Description
`id`required	path	The contact property id.

Request body

Field	Type
`fallback_value`required	`any`

Unknown fields are rejected, so a typo never silently does nothing.

Example

curl -X PATCH 'https://api.sendsend.email/v1/contact-properties/ID' \
  -H "Authorization: Bearer $SENDSEND_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "fallback_value": "starter"
}'

Response `200`

{
  "id": "prop_Lm4…",
  "object": "contact_property",
  "key": "plan",
  "type": "string",
  "fallback_value": "starter",
  "created_at": "2026-10-06T15:00:00.000Z"
}

Errors

Status	Code	When
400	`validation_error`	The request body or parameters are invalid. The message says which field.
404	`not_found`	No such resource in this project.
401	`unauthorized`	The API key is missing, invalid or revoked.
403	`forbidden`	The key does not have the scope this endpoint needs.

Every error has the same shape. See Errors.