What Is a Passkey? The Future of Passwordless Login

01What's the Problem with Passwords?

Passwords have been the basis of authentication for decades, but their weak points are well known: people choose short, guessable passwords, reuse the same password across many accounts and can easily type their password into a fake login page. When a site's database leaks, millions of passwords are put at risk at once.

Long passwords and password managers ease these problems considerably; we covered the details in our post on creating strong passwords. But one basic weakness remains: a password is a shared secret. Both you and the site know it, and it can be stolen anywhere it is typed.

Passkeys turn this approach around. There is no shared secret; the site holds the information it needs to verify you, but has nothing that would let anyone sign in on your behalf.

02How Do Passkeys Work?

Passkeys are based on public-key cryptography. When you create a passkey on a site, your device generates a key pair specific to that site. The private key stays on your device or in your password manager, which syncs it in encrypted form; the public key is sent to the site.

At login, the site sends a random challenge. Your device signs it with the private key, and the site verifies the signature with the registered public key. A fingerprint or face scan only unlocks the device at this point; your biometric data never leaves the device and is not sent to the site.

1. You tap the “Sign in with passkey” option on the site
2. The device verifies you with a fingerprint, face recognition or your screen-lock PIN
3. The private key signs the challenge sent by the site
4. The site checks the signature with the public key and opens the session

03What Is FIDO2?

FIDO2 is the family of open standards underlying passkeys. Developed jointly by the industry body FIDO Alliance and the W3C, which sets web standards, it has two parts: the WebAuthn interface the browser uses to talk to sites, and the CTAP protocol the device uses to talk to external authenticators (such as a USB security key).

Being an open standard is an important advantage. Because the major operating systems and browsers support the same standard, a passkey is not tied to a single company, and developers can serve all platforms through a single interface.

04Are Passkeys Secure?

Are passkeys secure? is one of the most common questions. The short answer: they are far more resilient than passwords, because there is no password to steal or guess. Even if a site's database leaks, the public keys that are captured are useless for getting into your account.

The biggest gain is phishing resistance. A passkey is bound to the domain it was created for; the browser never offers a site's passkey on a fake address. However careless the user is, they cannot “type” their key into a look-alike address. We covered how fake e-mails are put together in our post on what phishing is.

Things to Watch For

• Your device's screen lock must be strong; the fortress of a passkey is the device itself
• Protect the cloud account you use for synced passkeys with two-step verification
• Keep a backup passkey on a second device or a hardware key in case of device loss
• Account recovery routes (e-mail, backup codes) must be as secure as the passkey

05How Do You Use Passkeys?

On a site that supports them, you usually create a passkey in the security section of the account settings. When you tap “Create a passkey,” your device verifies you and the key is saved; from then on, a fingerprint or face scan is enough at login instead of a password.

Synced and Device-Bound Passkeys

Synced passkeys are carried to your devices linked to the same account through the encrypted vault of the operating system or password manager; they aren't lost when you change phones. Device-bound passkeys, on the other hand, live on a USB or NFC security key and never leave it; they are preferred for critical uses such as administrator accounts.

Signing In from Another Device

When you sign in on a computer that doesn't have your passkey, a QR code appears on the screen. When you scan it with your phone, the phone uses Bluetooth for a proximity check and approves the login. That way you get signed in on that computer without the key ever leaving your phone.

06Adding Passkeys to Websites

Adding passkeys to a site with a membership system is done with the browser's WebAuthn interface and a server-side library that verifies signatures. For every registration and login, the server generates a single-use challenge, verifies the response that comes back and stores the public key matched to the user record.

The example below shows the skeleton of a browser-side call to create a new passkey. The challenge and user ID come from the server; in a real project the response must always be verified on the server.

Passkey support is one of the easiest features to add to a membership system written from scratch; adding it to an existing setup later often requires rethinking session management. In custom software solutions where users sign in every day, such as hotel booking, an agency panel or a dealer portal, planning this feature at the start of the project improves both security and user satisfaction. Especially in businesses where staff sign in from shared computers, personal security keys also put an end to the habit of sharing passwords.

• During the transition, offer passkeys as an additional option alongside passwords and don't make them mandatory
• Design the passkey option on the sign-in screen to be simple and visible
• Let users add and delete multiple passkeys in account settings
• Build the recovery flow to be as secure as the passkey itself

const credential = await navigator.credentials.create({
  publicKey: {
    challenge: sunucudanGelenChallenge,
    rp: { name: 'Sample Company', id: 'ornek.com' },
    user: { id: kullaniciIdBytes, name: 'ayse@ornek.com', displayName: 'Ayse' },
    pubKeyCredParams: [
      { type: 'public-key', alg: -7 },
      { type: 'public-key', alg: -257 }
    ],
    authenticatorSelection: { residentKey: 'required', userVerification: 'preferred' }
  }
});

07The Future of Passwordless Login

As major platforms spread passkey support, passwordless login is moving from an experimental feature to an everyday option. Still, passwords won't disappear overnight; passkeys and passwords will live side by side for a long time.

For businesses, the right strategy is a gradual transition. First, passkeys or hardware keys are made mandatory for administrator and staff accounts; then they are offered to customers as an optional choice. As usage rates are monitored, password login is pushed to the background and the “I forgot my password” requests reaching the support team can also fall.

In the future of authentication, cryptography itself is changing too. We covered how new algorithms resistant to quantum computers will affect public-key systems like passkeys in our post on post-quantum cryptography.