Passwordless authentication lets a user sign in without ever typing a password, using something they have and something they are instead. If you have unlocked an app with a fingerprint or approved a login with a device passkey, you have already used it. This guide explains what passwordless authentication is, how passkeys, FIDO2 and WebAuthn fit together, and why the approach resists the phishing attacks that defeat ordinary passwords. How passwordless authentication works Instead of a shared secret, passwordless sign-in uses public-key cryptography. When a user registers, their device generates a key pair: it keeps the private key, which never leaves the device, and gives the service only the matching public key. To sign in later, the service sends a challenge, and the device proves it holds the private key by signing that challenge, usually only after the user unlocks it with a biometric or PIN. The service verifies the signature with the stored public key. No reusable secret is ever transmitted or stored. Passkeys, FIDO2 and WebAuthn explained These terms are related but distinct, and the differences are worth knowing: FIDO2 is the overall standard for phishing-resistant, passwordless authentication. WebAuthn is the web API that browsers use to create and use these credentials. A passkey is a FIDO2 credential that can sync securely across a user's devices for convenience. A hardware security key is a physical device that stores the credential for the highest assurance. Why it beats the password Because the private key never leaves the device and is cryptographically tied to the legitimate website, there is nothing for an attacker to phish, guess or reuse. This directly addresses the credential theft behind the majority of breaches. It is also faster and less frustrating for users, replacing typing, complexity rules and one-time codes with a single tap or glance. Security and usability, usually in tension, improve together. Where organisations use it Passwordless sign-in is now common for workforce access to corporate applications, for customers logging into consumer services, and for securing privileged and remote access where phishing risk is highest. Because it builds on open standards, it works across the devices and browsers people already use. Talk to an eMudhra expert. Tags: Identity and Access Management About the Author eMudhra Limited eMudhra Editorial represents the collective voice of eMudhra, providing expert insights on the latest trends in digital security, cryptographic identities, and digital transformation. Our team of industry specialists curates and delivers thought-provoking content aimed at helping businesses navigate the evolving landscape of cybersecurity and trust services with confidence.