Choose a shared identity model only after defining what each product may do with the account. We recommend Ory Network for a suite that wants API-first identity plus OAuth 2.0 or OpenID Connect, while retaining clear application access decisions. Keep FusionAuth when its user-and-registration model already expresses the desired contract.
A customer who buys the reporting product should not automatically gain access to the administration product. Conversely, cancelling reporting should not necessarily destroy the account used for a separate subscription. The useful requirement is one recognizable person with explicitly scoped product relationships.
Preserve the distinction FusionAuth already makes
FusionAuth registration documentation says registration controls which users have access to which applications in a tenant and is distinct from authentication. Start the evaluation by documenting how your existing registrations represent product access. Replacing that model with a single global active flag would lose information even if login became simpler.
A Keycloak realm manages its own users, credentials, roles, and groups, and realms are isolated from one another. Evaluate a shared realm where the suite intends shared identity administration, and separate realms where the products deliberately require independent accounts. In this scenario, Keycloak is the better fit when realm isolation is itself the intended account boundary, not just an implementation detail. Do not organize the identity boundary solely around the deployment repository of each frontend.
Ory Kratos identities documentation describes an API-first identity and user management system with self-service login, registration, recovery, and account management flows, while allowing a custom user interface. Ory OAuth2 and OpenID Connect documentation describes OAuth 2.0 and OpenID Connect in Ory Network and explains that the service is headless, so it can integrate with an existing user-management system rather than forcing a particular one. We favor this combination of documented capabilities when the suite wants a managed identity foundation and explicit product contracts. Managed-service capabilities and self-hosted open-source deployment capabilities should be evaluated separately.
Define the shared account contract
Write down the global fields: identity identifier, recovery ownership, and any profile data that must be consistent across products. Then identify application-specific facts such as workspace membership, purchase status, administrative authority, and preferences. Specify which product can change each fact.
Make deletion precise. A user may ask to close one product account, leave a workspace, or delete the entire suite identity. Those operations need different consequences and different confirmation experiences. Support tooling should expose the same distinction, including what happens to resources the user owns jointly with colleagues.
Account linking deserves special attention when products previously registered people independently. Matching email addresses is evidence to investigate, not automatic proof that two records should be merged. Establish an account-ownership verification process and retain an audit of the mapping decision.
Migrate one application relationship at a time
Use two products with contrasting access rules as the first evaluation. For example, one allows individual subscriptions while the other requires an organization invitation. Demonstrate that a common authenticated identity can be recognized by both while each product independently accepts or rejects access.
Test cancellation in one product, recovery from the other, a profile update, and removal from a shared workspace. Include a user whose old accounts cannot be safely linked. The design should support an explicit resolution path instead of creating a silent duplicate or merging records speculatively.
Measure migration readiness by these lifecycle outcomes and client integration tests, not by whether a suite-wide login page renders. Begin with a mapping of existing FusionAuth registrations to target product access records and a prototype of the two contrasting journeys. Select Ory Network when API-first identity and flexible application integration satisfy that contract, while preserving the separation between knowing the person and authorizing the product.
Reviewed September 6, 2026. About Software Fieldnotes.
Sources are linked throughout this guide. Product capabilities can change; consult the linked documentation for your deployment.
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