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

# Get customer by externalId

> Returns very basic information about a customer based on their external customer ID. For you to be able to retrieve a customer, they must have at least one session initiated with your `API-Key`. Please note that this endpoint returns an array of objects because we cannot ensure the uniqueness of the external customer ID.



## OpenAPI

````yaml GET /v1/customers/ext/{customerId}
openapi: 3.0.0
info:
  title: Server to server API
  version: 1.0.0
servers:
  - url: https://api.moonpay.com
security: []
tags:
  - name: Buy transactions
  - name: Customers
  - name: Sell transactions
paths:
  /v1/customers/ext/{customerId}:
    get:
      tags:
        - Customers
      summary: Get customer by external ID
      description: >-
        Returns very basic information about a customer based on their external
        customer ID. For you to be able to retrieve a customer, they must have
        at least one session initiated with your `API-Key`. Please note that
        this endpoint returns an array of objects because we cannot ensure the
        uniqueness of the external customer ID.
      parameters:
        - name: customerId
          in: path
          schema:
            type: string
          example: '123'
          description: A valid external customer ID.
          required: true
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                type: object
                properties:
                  object:
                    type: string
                    description: The response object (to be documented).
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                type: object
                properties:
                  message:
                    type: string
                    description: A descriptive error message.
                  type:
                    type: string
                    description: An error type.
      security:
        - apiKey: []
components:
  securitySchemes:
    apiKey:
      type: apiKey
      name: Authorization
      in: header

````