Yes, in most environments they should keep controlled fallback paths during migration, but those paths need explicit boundaries. The goal is to reduce password dependence over time, not to let fallback methods become the permanent primary control for customer authentication.
Why fallback passwords should be temporary, not the destination
During a passkey rollout, fallback is often a migration aid, not a long-term design goal. The control decision is about sequencing: keep a bounded recovery path so legitimate users are not stranded, but make sure the fallback is narrower, slower, and more heavily monitored than the passkey path. That keeps the authentication model moving toward phishing resistance instead of preserving password dependence.
Fallback also changes your assurance posture. A passkey flow can be strong while the fallback path becomes the weakest route into the account, so the real question is whether the fallback preserves enough friction, proof, and telemetry to avoid becoming the default attack path. Customer IAM teams usually need to treat the fallback as a controlled exception with a sunset plan, not as equal standing with passkeys.
For the identity and recovery mechanics behind that design, Customer IAM (CIAM) Guide is the closest navigation point because it covers passkeys, account recovery, and account-takeover resistance together. The migration question is not just whether a password exists, but whether the fallback path creates an easier recovery-abuse route than the primary sign-in path.
How to keep a fallback without recreating password risk
The right fallback is usually a recovery path with tighter limits, not a second full-strength sign-in method. In practice, that means avoiding broad password reuse, limiting the number of recovery attempts, requiring step-up checks where the risk is higher, and designing the flow so support agents cannot casually reset a user back into an ordinary password-based login.
It also matters which users the fallback serves. If you are supporting older devices, mixed-device households, or users still mid-enrollment, the fallback should help them complete migration, but it should not be the path of least resistance for high-value accounts. When a fallback is indistinguishable from normal login, users and attackers both learn that passkeys are optional.
Passwordless and Passkeys Guide is useful here because it ties passkey rollout to recovery design rather than treating passwordless sign-in as a purely front-end change. If the fallback can be abused to regain access with only weak verification, it has effectively undone much of the security gain from passkeys.
For customer environments, Workforce Identity Security Guide still offers a useful parallel lesson: recovery and reset flows are often where the security boundary weakens first. The same pattern appears in CIAM when help desk, account recovery, or secondary verification becomes easier to socially engineer than the original account sign-in.
What the migration phase changes for fraud, support, and assurance
Migration is the phase where attackers look for ambiguity. A customer who is part way through enrolling passkeys may still rely on password reset, SMS backup, email recovery, or support-assisted restoration, and each of those paths can become a fraud target. The more fallback methods you keep, the more important it becomes to understand which one is actually the highest-risk path in production.
That is why operational ownership matters. Product teams want adoption, support teams want low friction, and security teams want lower takeover risk. If no one owns the fallback sunset, the temporary exception becomes permanent, and the password path starts to define the real assurance level of the whole CIAM program.
NIST SP 800-63 Digital Identity Guidelines is relevant because passkey strength still depends on the surrounding authenticator and recovery model, not just the factor label. The practical lesson is to align fallback with the assurance target you actually need, rather than assuming any backup method is automatically acceptable once passkeys exist.
Risk and Threat Considerations
Fallback passwords extend the attack surface when they remain too broad, too durable, or too easy to reset. The common failure mode is not the passkey itself, but the recovery path becoming the easiest way to bypass the stronger primary authenticator, especially through phishing, credential stuffing, support abuse, or account recovery fraud.
Failure mechanism: Attackers target whichever route still accepts weaker proof, then use password reset, recovery, or support-assisted changes to regain a reusable secret that can survive beyond the passkey rollout.
Impact: Account takeover risk remains materially higher than the passkey design intended, and the organisation may keep a password-era fraud pattern alive under a passwordless label.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
NIST SP 800-63, OWASP ASVS and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-63 | IA-5 — Authenticator Lifecycle Management | Fallback passwords are part of authenticator lifecycle and recovery design. |
| IA-2 — Identification and Authentication | Customer sign-in assurance depends on the overall authentication method mix. | |
| IA-12 — Identity Proofing | Account recovery and re-enrollment depend on proofing strength when passwords are reduced. | |
| Recommendation — Limit password fallback duration and retire it as passkey adoption matures. Require the fallback path to preserve the intended assurance level for customer login. Tighten proofing before allowing fallback-based account recovery or reset. | ||
| OWASP ASVS | V6 — Authentication | Passkey rollout and fallback methods are authentication controls that need verification. |
| V10 — OAuth and OIDC | Customer identity journeys often use federation and recovery flows around the primary authenticator. | |
| Recommendation — Verify that fallback authentication is weaker and more constrained than passkey sign-in. Review recovery and reauthentication flows that sit beside the passkey journey. | ||
| NIST CSF 2.0 | PR.AA-05 — Managed Authentication Methods | Managed authentication methods should be constrained during migration from passwords to passkeys. |
| Recommendation — Manage fallback sign-in as a controlled exception and monitor its continued use. | ||
Practitioner Guidance
What to prioritise: Keep fallback focused on migration and recovery, not everyday login. If the fallback is available for normal sign-in, review whether it is still justified or whether it should be limited to exception handling only.
What to verify: Check that the fallback path has tighter assurance than the passkey path does, including step-up checks, rate limits, monitoring, and a clear retirement trigger. A fallback that is easier than the primary method is a design defect, not a convenience feature.
Common mistake: Teams launch passkeys but leave passwords in place with the same privilege, same support treatment, and no sunset date. That usually preserves the old risk model while adding a new one.
Practitioner takeaway: Keep fallback only long enough to move users safely to passkeys, then shrink its scope until it is clearly an exception path rather than a parallel authentication standard.