The LoginID iOS SDK enables passwordless authentication using FIDO2-certified biometric capabilities for user registration, authentication, and transaction confirmation. It integrates with Apple's Authentication Services framework and iCloud Keychain for secure passkey management, requiring iOS 15 or later and configuration of the apple-app-site-association file. The SDK provides methods for user authentication, sending codes, checking login status, and managing user sessions, though it does not persist sessions across app restarts. It supports PSD2 principles and offers tools for integration and scaling.