Passkey Implementation & Rollout (WebAuthn Level 3)

Plans, implements, and audits passkey sign-in for any web app and backend, based on WebAuthn Level 3 (a W3C Recommendation since 25 August 2026) and current browser documentation.

What it covers

• The irreversible decisions first: RP ID, opaque user handle, and the role passkeys play in your login.
• Registration and sign-in defaults, autofill (conditional UI) plus an explicit passkey button, with framework-neutral client code and JSON fallbacks.
• A complete server-side verification checklist: challenge, origin allow-list, RP ID hash, UP/UV flags, credential ownership, signature, and sign-counter handling that does not lock out synced passkeys.
• Level 3 features with feature detection and fallbacks: automatic password-to-passkey upgrades (conditional create), the Signal API, Related Origin Requests, client hints, and native JSON helpers.
• A phased rollout plan with metrics and a rollback trigger, a recovery matrix for lost devices, UX copy, and support macros.
• An audit mode that reports each check as PASS, FAIL, or NOT FOUND with file and line evidence.

Works with any stack; includes library options for Node.js, PHP/Laravel, Python, Go, Java, .NET, Ruby, and Rust. Official sources are cited in the package.