If you've set up a new Windows machine recently, you've been nudged toward using a PIN instead of your Microsoft account password. That probably felt like a downgrade. A PIN is shorter, simpler, and looks a lot like the kind of thing security advice tells you to avoid.
The reason it's actually more secure has to do with where the credential lives — not how complex it is.
The problem with passwords
When you sign in to Windows with your Microsoft account password, that password is sent to Microsoft's servers to be verified. This creates attack surface: the password travels over a network, it's stored somewhere remotely, and if Microsoft's infrastructure is ever compromised — or if the same password is reused somewhere else that gets breached — your account is at risk.
More practically, passwords can be stolen through phishing, keyloggers, or credential stuffing attacks using passwords leaked from other services.
What Windows Hello does differently
Windows Hello stores your credential — whether it's a PIN, fingerprint, or face scan — directly on the device, in a dedicated hardware chip called the Trusted Platform Module (TPM). The credential never leaves your machine. When you sign in, Windows verifies your identity locally; nothing is transmitted to Microsoft's servers for that verification step.
This means if an attacker steals your PIN, it's useless to them without also physically having your device. You can't use someone's PIN to sign in remotely or on a different machine the way you can with a stolen password.
Why this matters in practice
The most common way accounts get compromised isn't a targeted attack on you specifically — it's automated attacks using credentials harvested from unrelated data breaches. A leaked password from a breached website gets tried against email accounts, Microsoft accounts, bank logins. Windows Hello breaks this entirely: your PIN works only on your device, so a credential breach somewhere else can't be used against your Windows login.
The PIN length is almost beside the point. A four-digit PIN that's hardware-bound to one device is harder to exploit at scale than a twelve-character password that travels over the network.
Biometrics are the same idea
Fingerprint and face recognition in Windows Hello work on the same principle. The biometric template is stored in the TPM and never leaves the device. This is worth knowing if you've had concerns about Microsoft storing a scan of your face somewhere — they don't. The verification happens locally.
If your hardware supports it, fingerprint or face login is worth enabling. The combination of local credential storage and the convenience of not typing anything at all is one of the better security improvements available with no real tradeoff.