# Link user IDs via external ID

Links a user from your game to a user from your Login project via an external ID. You will not be able to link the same external ID to different users and update the external ID of a user if they already have it.

You can find an external ID in:
* a user JWT after successful authentication as a value of the external_account_id claim,
* a response of the Get user details call as a value of the external_id parameter.

Endpoint: POST /users/account/link_external_id
Version: v1
Security: Server

## Request fields (application/json):

  - `external_account_id` (string, required)
    User ID from your game. Used as an external ID by which users will be linked.
    Example: "A1234BB23"

  - `user_id` (string, required)
    The Xsolla Login user ID. You can find it in Publisher Account > your Login project > Users > Username/ID.
    Example: "6bd371c2-8044-11e9-b0a8-39deff2bb627"

## Response 400 fields (application/json):

  - `error` (object, required)

  - `error.code` (string, required)
    Error code.
    Example: "003-061"

  - `error.description` (string, required)
    Error description.
    Example: "Object not found."

  - `error.details` (object)
    Additional information.

## Response 401 fields (application/json):

  - `error` (object, required)

  - `error.code` (string, required)
    Error code.
    Example: "003-061"

  - `error.description` (string, required)
    Error description.
    Example: "Object not found."

  - `error.details` (object)
    Additional information.

## Response 404 fields (application/json):

  - `error` (object, required)

  - `error.code` (string, required)
    Error code.
    Example: "003-061"

  - `error.description` (string, required)
    Error description.
    Example: "Object not found."

  - `error.details` (object)
    Additional information.

## Response 422 fields (application/json):

  - `error` (object, required)

  - `error.code` (string, required)
    Error code.
    Example: "003-061"

  - `error.description` (string, required)
    Error description.
    Example: "Object not found."

  - `error.details` (object)
    Additional information.

## Response 429 fields (application/json):

  - `error` (object, required)

  - `error.code` (string, required)
    Error code.
    Example: "003-061"

  - `error.description` (string, required)
    Error description.
    Example: "Object not found."

  - `error.details` (object)
    Additional information.


## Response 200 fields