Passwords fail in predictable ways: they are reused, guessed, phished, and leaked in breaches. Most of the advice to fix this — longer passwords, a manager, codes from an app — helps, but one category of attack survives all of it. Phishing.
Why codes are not enough
A one-time code from a text or an authenticator app proves you have the code right now. It does not prove which site you are giving it to. A convincing fake login page can collect your password and your code in real time and replay them. That is the gap.
What a security key changes
A hardware security key uses public-key cryptography bound to the real website's address. When you register, the key stores a secret it never reveals; when you sign in, it proves possession only to the legitimate site. A phishing page has the wrong address, so the key simply will not respond. The attack does not fail at the last step — it never starts.
Passkeys, briefly
Passkeys apply the same cryptography, stored on your phone or computer instead of a separate device. They are a major improvement over passwords for everyday accounts. A dedicated hardware key adds a physical factor that does not live on a device that can be remotely compromised — useful for the accounts that matter most.
Where to start
Add a security key or passkey to your email and password manager first — the accounts that can reset everything else. Keep a backup key in a safe place. You will still use passwords for a while; the point is to remove them as the single thing standing between an attacker and your account.
Hardware authentication is not exotic. It is the rare security upgrade that makes the common attack stop working.