Passkeys and WebAuthn: The Complete Guide to Killing Passwords in Your Web App

Your users are still typing passwords. In 2026. Despite every major platform — Apple, Google, Microsoft — shipping passkey support, most web applications are still stuck on the same authentication architecture from 2005: hash a password, store it in a database, pray nobody finds it. The reason isn't that passkeys are hard to understand. It's that the implementation path is littered with undocumented pitfalls, confusing specifications, and a WebAuthn API that looks simple in demos but breaks in production. What does allowCredentials actually do? Why does navigator.credentials.get() silently fail on some browsers? How do you migrate 500,000 existing users without breaking their sessions? This guide covers everything you need to ship passkeys in production — from the cryptographic fundamentals to complete TypeScript implementations, Conditional UI integration, database schema design, multi-device sync, and the phased migration strategy that lets you transition without forcing users to cha