Every app I audit has the same two authentication problems: users abandon signup at the password screen, and the SMS OTP bill grows linearly with success. Passkeys — the industry-standard replacement for passwords built on FIDO2/WebAuthn — solve both, and by 2026 the platform support is mature enough that I now recommend them as the default for new consumer apps. Here is what that means in practice.
What a Passkey Actually Is
A passkey is a cryptographic key pair. The private key lives on the user's device, protected by the same biometric or screen lock they already use; the public key lives on your server. Signing in means the device proves possession of the private key — one fingerprint or face scan, no typing. There is nothing to phish (no shared secret crosses the network), nothing to reuse across sites, and nothing to leak in a database breach except public keys, which are useless to an attacker.
Why Users Actually Care
Not because of security — users never adopt anything for security. They care because sign-in becomes one biometric prompt. No 'create a password with one uppercase, one symbol...', no waiting for an SMS that arrives late, no password-reset flows. In funnel terms: every field you remove from onboarding recovers abandoned users, and passkeys remove the worst fields. The security win is real but it's the conversion win that pays for the work.
The Cross-Device Story Finally Works
The historical objection — 'what if the user loses their phone?' — is answered by synced passkeys: Google Password Manager syncs them across a user's Android devices and Chrome, iCloud Keychain across Apple devices, and cross-ecosystem sign-in works by scanning a QR code with the phone that holds the key. It is not perfect for users who straddle ecosystems, which is why account recovery still needs a fallback — but the everyday experience is now smooth enough for mainstream users.
Implementation on Android, iOS, and Flutter
On Android, the Credential Manager API is the single entry point — it handles passkeys, saved passwords, and federated sign-in through one dialog. On iOS, passkeys ride on the AuthenticationServices framework with ASAuthorizationPlatformKeyCredential. In Flutter, mature plugins wrap both platform APIs, so the passkey ceremony stays native while the surrounding flow is shared Dart. Server-side, any WebAuthn library works — the mobile side is standard FIDO2. The genuinely hard part is not the crypto ceremony; it's the product design around it.
The Migration Strategy That Works
Do not force-migrate existing users — that burns goodwill. The pattern that works: new users get passkey-first signup with email fallback; existing users get a one-tap 'switch to passkey' prompt after a successful password login, when trust is highest; and passwords remain valid until the user chooses to drop them. Measure passkey adoption monthly. When your active users are majority-passkey, you can start deprecating passwords for real. Expect that to take a year, not a quarter.
What It Costs and Saves
Adding passkey support to an existing app with a standard auth backend is typically 2–4 weeks of work — ₹1.5–3 lakhs at my rates depending on how tangled the existing auth is. Against that: SMS OTP costs of ₹0.15–0.25 per message disappear for passkey users, password-reset support tickets drop, and signup conversion improves. For an app sending a few lakh OTPs a month, the integration pays for itself within the year on SMS savings alone.
Should Your App Adopt Passkeys in 2026?
New consumer app: yes, passkey-first from day one — retrofitting is always more expensive. Existing app with SMS OTP costs that hurt: yes, and the finance team will thank you. Enterprise app behind SSO: your identity provider likely handles it — check before building anything. Banking and fintech: yes, but as part of a broader strong-authentication review, not a bolt-on. If you want a scoped estimate for your specific auth setup, describe it in the contact form — auth migrations are among the most predictable projects I quote.