Definition
Web Authentication: An API for accessing Public Key Credentials - Level 3 defines Base64URLString
typedef DOMString Base64URLString;Referring IDL interfaces/dictionaries
AllAcceptedCredentialsOptionsAuthenticationResponseJSONAuthenticatorAssertionResponseJSONAuthenticatorAttestationResponseJSONCurrentUserDetailsOptionsPublicKeyCredentialCreationOptionsJSONPublicKeyCredentialDescriptorJSONPublicKeyCredentialRequestOptionsJSONPublicKeyCredentialUserEntityJSONRegistrationResponseJSONUnknownCredentialOptions