> ## Documentation Index
> Fetch the complete documentation index at: https://www.plain.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# upsertCustomer

> Creates or updates a customer identified by email address, external ID, or Plain customer ID.
Supply `onCreate` fields for values to set when creating and `onUpdate` fields for values to
apply when the customer already exists. The output's `result` field indicates whether the
customer was `CREATED`, `UPDATED`, or `NOOP` (existed and no values changed). Requires the
`customer:create` and `customer:edit` permissions.