Passkeys Explained: What They Are and When to Use Them

Passkeys Explained: What They Are and When to Use Them

Passkeys explained simply: passkeys represent the most significant shift in everyday authentication in decades, and understanding what passkeys are — and when to use them — is increasingly practical knowledge for anyone who manages online accounts. Unlike passwords, which are shared secrets between you and a website, passkeys use cryptographic key pairs to verify your identity without ever transmitting a secret across the internet. This article explains how passkeys work, what makes them different from existing alternatives, and how to evaluate when using a passkey is the right choice for a given account.

The Technical Foundation: Public Key Cryptography Without the Complexity

Passkeys are built on a standard called WebAuthn, which is part of the FIDO2 specification developed by the FIDO Alliance and the World Wide Web Consortium (W3C). You do not need to understand the cryptography in depth to use passkeys effectively, but a basic mental model helps explain why they are fundamentally more secure than passwords.

When you create a passkey for an account, your device generates a pair of mathematically linked cryptographic keys: a private key that never leaves your device, and a public key that is sent to and stored by the website. When you log in, the website sends a cryptographic challenge to your device. Your device uses your private key to sign the challenge and sends back the signature — not the key itself. The website verifies the signature using the public key. At no point does a password or shared secret cross the network.

This design eliminates several entire categories of attack. Phishing attacks that trick you into entering a password on a fake site cannot capture a passkey, because the passkey is cryptographically bound to the legitimate domain. Server-side data breaches cannot expose passkeys, because the website only stores a public key — which is worthless without the private key on your device. Credential stuffing attacks — automated attempts to use leaked password lists — have nothing to stuff, because there is no password to leak.

The FIDO Alliance maintains comprehensive documentation on the passkey standard at FIDOAlliance.org — Passkeys. This is the primary industry standards body for the underlying technology.

How Passkeys Are Stored and Synced

Passkeys can be stored in two ways: bound to a specific hardware device (a hardware security key or a device’s secure enclave), or synchronized across devices through a cloud credential manager.

Synced Passkeys

Most consumer passkey implementations use synchronized passkeys, stored in a platform credential manager. Apple stores synced passkeys in iCloud Keychain; Google stores them in Google Password Manager; and third-party password managers like 1Password and Bitwarden have added passkey support. A synced passkey is accessible from any device signed in to the same account — so if you create a passkey on your iPhone, you can also use it on your iPad or Mac without any additional setup.

Synced passkeys provide excellent convenience for most consumer use cases. Their security depends partly on the security of the cloud account holding the sync — which is one reason strong account security (a strong passphrase and a hardware security key) on your iCloud, Google, or password manager account is particularly important if you rely on synced passkeys.

Device-Bound Passkeys

Device-bound passkeys remain on the specific hardware where they were created — typically a FIDO2 hardware security key or a device’s built-in secure enclave — and cannot be exported or synced. They offer the highest assurance for high-stakes accounts: financial institutions, enterprise systems, and accounts where account compromise would have severe consequences. The tradeoff is that if you lose the device, you will need to use backup authentication methods to recover access. Hardware security keys designed for FIDO2, such as those meeting the FIDO Certified standard, support device-bound passkeys.

Passkeys vs. Other Authentication Methods

Passkeys are frequently compared to other modern authentication approaches. Understanding the distinctions helps you make informed decisions about which accounts to prioritize.

Passkeys vs. Passwords

Passwords are shared secrets that can be guessed, phished, leaked in a breach, reused across sites, or intercepted in transit if a site fails to implement transport security properly. Passkeys have none of these vulnerabilities. They cannot be guessed (the private key is not humanly memorable), cannot be phished (domain-binding prevents fake sites from completing authentication), cannot be leaked from the server (the server never has the secret), and cannot be reused across sites (each passkey is site-specific). For any account where a passkey option is available, it is a meaningfully stronger choice than a password alone.

Passkeys vs. Passwords Plus Two-Factor Authentication (2FA)

Passwords combined with app-based 2FA (such as a time-based one-time password from an authenticator app) are substantially more secure than passwords alone — but they remain vulnerable to real-time phishing attacks, where an attacker intercepts both your password and your 2FA code by proxying your session to the real site. Passkeys resist this attack because the cryptographic binding to the site’s domain means the authentication cannot be replayed on a different domain.

This does not mean TOTP-based 2FA is without value — it is still a strong upgrade from passwords alone, and many sites do not yet support passkeys. But for accounts that support passkeys, they offer a security profile that is generally superior even to passwords plus TOTP.

Passkeys vs. SMS-Based One-Time Codes

SMS-based one-time codes are the weakest common form of second-factor authentication, because they are vulnerable to SIM-swapping attacks, interception, and social engineering of mobile carriers. Passkeys entirely replace this mechanism for sites that support them, and are a significant security upgrade over any SMS-based flow.

When to Use a Passkey

Passkeys are appropriate for any account where the option is available and you have confidence in your sync ecosystem’s security. High-priority accounts to migrate first include:

• Email accounts: Your email is the recovery mechanism for most of your other accounts. A compromised email account can cascade into compromise of nearly everything else. Passkeys for email accounts are a high-priority upgrade.
• Financial accounts: Banks, brokerage accounts, and payment services that support passkeys should be migrated promptly.
• Social media and identity providers: Accounts used to log in to other services (Google, Apple, Microsoft) have an outsized impact on your overall security posture.
• Cloud storage and document services: Accounts containing sensitive personal or professional data.

CISA (the Cybersecurity and Infrastructure Security Agency) has published guidance on phishing-resistant multi-factor authentication, which covers passkeys and hardware security keys as the strongest options currently available. Their resources are available at CISA.gov — Multi-Factor Authentication.

When Passkeys May Not Be the Right Choice

Despite their security advantages, passkeys are not without practical considerations. Understanding when they may introduce friction helps you make reasonable tradeoffs.

• Shared accounts: If multiple people share a single account login (a household streaming service, a shared business account), passkeys complicate the sharing model because the private key is device-specific. Shared accounts may be better served by a shared password manager entry until the passkey ecosystem develops broader multi-user support.
• Accounts you access from many unrelated devices: If you need to access an account from devices that are not part of your personal device ecosystem (a public library computer, a colleague’s laptop), synced passkeys may require fallback to a password for those sessions, depending on the site’s implementation.
• Sites with immature passkey implementations: Some early passkey rollouts have limitations in account recovery, device management, or the ability to remove passkeys you no longer want. Before fully relying on a passkey, verify that the site provides a clear recovery path if you lose access to your device.

Setting Up Your First Passkey: What to Expect

The process of creating a passkey varies slightly by platform, but the general flow is consistent. Navigate to the security settings of a supported account. Look for an option labeled “Passkey,” “Sign-in with a passkey,” or similar. Your browser or device will prompt you to verify your identity (via your device’s biometric, PIN, or device passcode). Once verified, the passkey is created and stored in your credential manager. On subsequent logins, you will see an option to use a passkey rather than entering a password.

Most platforms that support passkeys do not require you to delete your password immediately. You can add a passkey while keeping your existing password as a backup — a reasonable approach while you build confidence in the new system.

The Broader Passkey Ecosystem

Passkey support is growing rapidly. Major platforms including Apple, Google, Microsoft, GitHub, PayPal, Adobe, and many others now support passkeys for consumer accounts. The FIDO Alliance maintains an up-to-date directory of websites and apps that support passkeys at their passkeys.dev resource. Browser support is mature across Chrome, Safari, Firefox, and Edge. The standards-based nature of passkeys — built on open FIDO2 and WebAuthn specifications — means implementations from different vendors are interoperable at the protocol level, even as the user experience varies.

Passkeys are not yet universally supported, and passwords will remain part of the authentication landscape for some years. But for accounts where the option is available, passkeys offer a concrete, practical security improvement that requires no ongoing user behavior change after setup — which is one of the strongest arguments in their favor.