Note that BankID was originally made available for merchants via a locally installed BankID Server software with its proprietary API. This is today referred to as the legacy integration option. The preferred integration option going forward is to make use of BankID via the OpenID Connect Provider (OIDC) from BankID. Please consult technical documentation on the OIDC Provider in general and the BankID service in particular for further information.
For product litterature on the BankID Service, please see the set of documentation (and in particular the White Paper) in the latest release of the BankID legacy integration package.