Use this when someone who already has a user on another identity needs access to yours, such as the same person acting for a second company.

It links the user identified by the user_id path parameter to the logged-in identity. Their credentials already exist, so no invitation is sent and no password is set. The user has access immediately and picks the identity they want to act for when they sign in. See List identities.

Choosing between linking and inviting

Use this for a user that already exists elsewhere on the platform. For someone new, register them with Register a user and send an invitation with Invite a user instead.

Conflicts

USER_ALREADY_LINKED_TO_IDENTITY means the user can already access this identity, so no action is needed. CREDENTIAL_NOT_FOUND means there is no user to link, so register one instead. KYB_MISSING, PROFILE_MISMATCH, and EMAIL_DOMAIN_NOT_ALLOWED mean the identity or the user isn't eligible for linking.

Access

This operation requires a stepped-up access token. Step up before calling it by issuing a challenge through Step-up.