What is my Tenant ID?
Resolve a domain to its Microsoft Entra ID tenant — or go the other way and look up what's behind a tenant ID. Runs in your browser.
◆ What is a tenant ID?
Every Microsoft 365 / Entra ID organisation has a unique tenant ID — a GUID like 72f988bf-…-2d7cd011db47. It identifies the directory behind sign-in, Conditional Access, guest invites and app registrations.
◆ How the forward lookup works
We read the tenant's public discovery document at /{domain}/v2.0/.well-known/openid-configuration and take the tenant GUID from its issuer — the same data Microsoft exposes at every sign-in.
◆ How the reverse lookup works
The same discovery endpoint accepts a GUID, which confirms the tenant exists and returns its region scope. The organisation's default domain and name come from Microsoft Graph's findTenantInformationByTenantId.
◆ When you'd need it
Cross-tenant access policies, B2B guest sharing, Conditional Access scoping, PowerShell and Graph automation, or tenant-to-tenant migrations — all of them reference the tenant by its ID.
No tracking · no accounts · lookups go straight from your browser to Microsoft