Use a hybrid model and separate the systems that can absorb passkeys from the ones that still require passwords or other federated methods. Keep the migration scoped to the applications, user groups, and recovery workflows you can govern end to end, and avoid a broad rollout that leaves support and compliance gaps.
How to Handle a Partial Passkey Environment
Teams should treat passkeys as the preferred path where they are technically supported, while keeping a controlled fallback for the applications, user populations, and recovery workflows that are not ready yet. The goal is not a perfect one-step migration; it is to narrow password exposure without breaking access, support, or governance.
The practical mistake is to assume that “passkeys are available” means they can replace every sign-in path at once. In reality, support varies by application, device state, browser capability, identity provider behavior, and account recovery design, so migration scope has to follow operational reality.
Why Hybrid Sign-In Is Usually the Right Transition Pattern
A hybrid model lets teams move fast where passkeys deliver the most value, while keeping federated sign-in or passwords available only where they remain necessary. That reduces the blast radius of migration issues and avoids forcing weak emergency workarounds into the same control plane as the new authentication method.
For most organisations, the useful unit of change is not “the whole workforce,” but a specific application set plus a defined user group with known device support and recovery requirements. If an app cannot handle passkeys cleanly, it should remain in the supported fallback path until the surrounding dependencies are upgraded.
Passkey rollout also changes recovery design. If users can enrol passkeys but cannot recover access without an unsafe bypass, the migration has not improved security end to end. The transition plan should therefore include lost-device handling, help desk procedures, and step-up or backup authentication rules before broadening scope.
Where Migration Should Be Scoped First
Start with systems that can absorb the full lifecycle: enrolment, sign-in, recovery, deprovisioning, and audit evidence. That usually means a limited set of applications with modern authentication support, a known device population, and a support team that can handle exceptions without creating ad hoc access paths.
Teams should also segment by risk and governance burden. Customer-facing or low-impact applications can be easier early candidates than systems with complex regulatory controls, high-availability constraints, or tightly scripted service workflows. The right first wave is the one you can govern cleanly, not the one with the broadest theoretical compatibility.
In parallel, keep passwords or federated methods only where they remain needed, and document exactly why each exception exists. That makes it easier to retire the fallback later and prevents temporary compatibility gaps from becoming permanent policy drift.
Risk and Threat Considerations
Hybrid authentication reduces migration risk, but it also creates a split control environment that attackers and users can exploit if the boundaries are vague. The main danger is not passkeys themselves, but inconsistent fallback handling, especially when legacy sign-in or recovery paths are easier to abuse than the new method.
Failure mechanism: Weak exceptions, broad recovery shortcuts, or uneven application support can leave the old authentication path as the easiest way in, even after passkeys are introduced. That creates a false sense of security while preserving the same account-takeover exposure the migration was meant to reduce.
Impact: Organisations can end up with fragmented assurance, poor auditability, and help desk processes that silently reintroduce phishing-resistant bypasses. The result is a partial deployment that improves user experience for some users but leaves material identity risk unchanged for others.
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 and NIST SP 800-53 Rev 5 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-63 | Digital Identity Guidelines | Passkeys, AAL, and phishing-resistant authentication are central to staged migration. |
| Recommendation — Align rollout and recovery with AAL guidance and phishing-resistant authenticator requirements. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Migration scope depends on provisioning, rotation, recovery, and retirement of authenticators. |
| IA-2 — Identification and Authentication (Organizational Users) | Hybrid sign-in for workforce users depends on controlled authentication choices by user population. | |
| IA-9 — Service Identification and Authentication | Applications and federated paths must be governed where system-to-system sign-in remains in use. | |
| Recommendation — Apply IA-5 to govern authenticator lifecycle and remove unsafe fallback paths. Use IA-2 to define which workforce users authenticate with passkeys versus legacy methods. Apply IA-9 to secure service and federated authentication paths that remain in the fallback model. | ||
| ISO/IEC 27001:2022 | A.5.16 — Identity management | Scoped migration needs controlled identity lifecycle ownership across supported and unsupported systems. |
| Recommendation — Define identity ownership and transition exceptions for each in-scope application and user group. | ||
Practitioner Guidance
What to prioritise: Define which applications, user groups, and recovery flows are in scope before announcing the rollout. The first pass should cover the systems where you can prove end-to-end control, not the systems where passkeys are merely convenient.
What to verify: Confirm that every fallback path is intentional, time-bounded, and reviewed, with clear ownership for when it can be removed. If support staff can override the new method more easily than users can use it, the migration needs tighter guardrails.
Decision rule: If a workflow cannot handle passkeys plus recovery without a special-case bypass, treat it as outside the initial migration wave. If it can be governed cleanly, move it first and use the result to build the next rollout cohort.
Practitioner takeaway: The best transition strategy is not “passkeys everywhere as soon as possible,” but “passkeys wherever they can be operated safely, with legacy methods contained and explicitly retired on a controlled timeline.”