WIwithflex
Customers

Create or update a customer

Changed on

Creates a customer. This endpoint upserts by email: if a customer with the same email already exists, that customer is updated with the supplied values instead of a new one being created. A customer.created webhook event is fired only when a new customer is created (not on update). If checkout_session_id is provided, the referenced checkout session is updated to reference this customer; it must belong to the authenticated account, otherwise the request is rejected with a 422 and no customer is created or updated.

post/v1/customers

Request

  • Base URL
    https://api.withflex.com
  • URL
    https://api.withflex.com/v1/customers
  • Auth
    HTTP bearer

Request body

Example request

{
  "customer": {
    "first_name": "John",
    "last_name": "Doe",
    "email": "joh.doe@example.com",
    "phone": "+15555555555",
    "employer": "Flex",
    "shipping": {
      "line1": "123 Main St",
      "line2": "Suite 100",
      "city": "San Francisco",
      "state": "CA",
      "postal_code": "94107",
      "country": "US"
    },
    "checkout_session_id": "fcs_01J9XR8M3K7VZ8N2YB4WJ6T0RA",
    "metadata": "{\"key\": \"value\"}"
  }
}

Response

An envelope wrapping a single customer object.

Example response

{
  "customer": {
    "customer_id": "fcus_01HACM7FZ1084XB1GB6053VM0D",
    "owner_partner_id": "obj_01J9XR8M3K7VZ8N2YB4WJ6T0RA",
    "first_name": "John",
    "last_name": "Doe",
    "email": "joh.doe@example.com",
    "phone": "+15555555555",
    "employer": "Flex",
    "shipping": {
      "shipping_address_id": "fsh_01J9XR8M3K7VZ8N2YB4WJ6T0RA",
      "line1": "123 Main St",
      "line2": "Suite 100",
      "city": "San Francisco",
      "state": "CA",
      "postal_code": "94107",
      "country": "US"
    },
    "metadata": {
      "order_id": "8842",
      "channel": "shopify"
    },
    "created_at": "2026-06-15T14:30:00Z",
    "test_mode": false
  }
}

Changes