OAuth 'Sign in with Google' round trip prevents password sharing, enhances security

The OAuth protocol's redirect process for services like 'Sign in with Google' exists to prevent users from sharing passwords with third-party sites. Instead, the site redirects you to Google, where you authenticate and approve specific permissions. The site then receives a time-limited, scoped access token, not your password. This system allows users to revoke access later and protects against compromised passwords, though users must still be cautious about approving malicious apps at the consent screen.