responseMode

OAuth 2.0 Responses: OPTIONAL. Informs the Authorization Server of the mechanism to be used for returning Authorization Response parameters from the Authorization Endpoint. This use of this parameter is NOT RECOMMENDED with a value that specifies the same Response Mode as the default Response Mode for the Response Type used.

OIDC SIOPv2: This response mode post is used to request the Self-Issued OP to deliver the result of the authentication process to a certain endpoint using the HTTP POST method.