OAuth2 (Open Authorization 2.0) is an industry-standard security protocol that allows users to grant applications limited access to their accounts without sharing passwords. When you click 'Sign in with Google' on a website, OAuth2 manages the secure connection. The protocol issues temporary access tokens rather than exchanging actual credentials, reducing security risks if one application is compromised. Municipal digital services may use OAuth2 to allow residents to sign in using existing accounts from trusted providers, simplifying access while maintaining security. Understanding OAuth2 helps explain how modern applications securely connect and why 'Sign in with...' buttons appear on many websites.