Security
What is Authentication?
The process of verifying the identity of a user or system.
Definition
Authentication (AuthN) verifies that a user is who they claim to be. Common methods include: passwords, multi-factor authentication (MFA), OAuth 2.0 / OpenID Connect (social login), magic links, passkeys/WebAuthn, and API keys. Authentication answers 'Who are you?' — distinct from authorization ('What can you do?'). Modern implementations use JWTs or session cookies to maintain authenticated state.