Is the Entra User ID unique per tenant or globally unique?

Question

I am looking for clarification on the uniqueness of the Entra User ID for a user : https://learn.microsoft.com/en-us/graph/api/resources/user?view=graph-rest-1.0. Is the ID unique only per tenant or globally unique across all tenants?

Answer 1

The Entra User ID is unique per tenant. It is not globally unique across all tenants.

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References:

• Microsoft Entra identity and network access API overview
• Microsoft Entra ID Guide for independent software developers

Answer 2

Hi @Harsha Iranna Dalali ,

I assume you are referring to the object ID/oid attribute. If this is the case, the oid claim or ObjectId property is immutable and unique, so it will uniquely identify the relevant directory object. When a single user resides in multiple Entra ID tenants, the user will contain a different object ID/oid in each tenant. They are considered as different accounts, even though the users log in to each account with the same credentials. So it is unique to both the tenant and across tenants.

If you're referring to the email address/User ID used to sign into Microsoft 365 (******@contoso.partner.onmschina.cn), this could exist in multiple tenants.

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