Hi @Loic Emissan ,
Microsoft Graph Users API is available to query details of the guest users of your M365 tenant and it will return the available information of the guest user from Azure AD (as shown below). Microsoft Graph Users API retuns both guest users added/created in your tenant and external users invited to your tenant. Also, Graph Beta Users API is providing some more guest user's details compared to V1.0. Please note that APIs under the /beta version in Microsoft Graph are subject to change. Use of these APIs in production applications is currently not supported by Microsoft. You can verify the below API and see if it is useful for you.
GET https://graph.microsoft.com/v1.0/users?$select=Id,userPrincipalName,userType,displayName,mail,accountEnabled,creationType,externalUserState&$filter=userType eq 'Guest'
Note : "userType" property can be returned only on applying $select OData query option with V1.0 Graph API.
GET https://graph.microsoft.com/beta/users?$filter=userType eq 'Guest'
GET https://graph.microsoft.com/beta/users/{id | userPrincipalName}
GET https://graph.microsoft.com/v1.0/users/{id | userPrincipalName}
Note: Please note that APIs under the /beta version in Microsoft Graph are subject to change. Use of these APIs in production applications is currently not supported by Microsoft.
Documentation Sources :
https://learn.microsoft.com/en-us/graph/api/user-get?view=graph-rest-1.0&tabs=http
https://learn.microsoft.com/en-us/graph/api/resources/user?view=graph-rest-1.0
Hope this helps.
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