OAuth2 (https://developer.okta.com/blog/2017/06/21/what-the-heck-is-oauth) is a protocol for stateless authentication and authorization. The protocol allows applications to obtain limited access to user accounts on services. User authentication is delegated to a service, typically an OAuth2 server. OAuth2 is more complicated to set up when compared to the previously mentioned mechanisms. JHipster supports setting up OAuth with OpenID Connect (OIDC) and can use Keycloak (https://keycloak.org) or Okta (https://developer.okta.com/blog/2017/10/20/oidc-with-jhipster) out of the box.