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// graph-permissions · Calendars

Calendars.ReadMicrosoft Graph permission · High risk

Allows the app to read events of all calendars without a signed-in user.

Application permission

High risk

Read calendars in all mailboxes. Allows the app to read events of all calendars without a signed-in user.

ID798ee544-9d2d-430c-a058-570e29e34338
ConsentAlways needs admin consent
RiskAs an application permission this reaches every user's data in the tenant, without anyone signed in.

Delegated permission

Medium risk

Read user calendars . Allows the app to read events in user calendars.

ID465a38f9-76ea-45b9-9f34-9e8b0d4b0b42
ConsentUsers can consent, if your consent settings allow it
RiskReads or changes the signed-in user's content, limited to what that user can access.

Least-privilege alternative

If you only need free/busy information, consider Calendars.ReadBasic where available.

Grant it to an app

In the portal: App registrations › your app › API permissions › Add a permission › Microsoft Graph › Application permissions, then grant admin consent. Or with Graph PowerShell:

powershell5 lines
Connect-MgGraph -Scopes "Application.Read.All", "AppRoleAssignment.ReadWrite.All"
$graph = Get-MgServicePrincipal -Filter "appId eq '00000003-0000-0000-c000-000000000000'"
$app   = Get-MgServicePrincipal -Filter "appId eq '<your app's client id>'"
New-MgServicePrincipalAppRoleAssignment -ServicePrincipalId $app.Id `
    -PrincipalId $app.Id -ResourceId $graph.Id -AppRoleId "798ee544-9d2d-430c-a058-570e29e34338"

Ask for it when signing in

Delegated permissions act as the signed-in user, so the app can never do more than that user can.

powershell1 line
Connect-MgGraph -Scopes "Calendars.Read"

Which apps already have it?

powershell6 lines
# Apps that hold Calendars.Read as an application permission
Connect-MgGraph -Scopes "Application.Read.All"
$graph = Get-MgServicePrincipal -Filter "appId eq '00000003-0000-0000-c000-000000000000'"
Get-MgServicePrincipalAppRoleAssignedTo -ServicePrincipalId $graph.Id -All |
    Where-Object AppRoleId -eq "798ee544-9d2d-430c-a058-570e29e34338" |
    Select-Object PrincipalDisplayName, PrincipalId, CreatedDateTime
powershell6 lines
# Apps with delegated consent for Calendars.Read
Connect-MgGraph -Scopes "Application.Read.All", "Directory.Read.All"
$graph = Get-MgServicePrincipal -Filter "appId eq '00000003-0000-0000-c000-000000000000'"
Get-MgOauth2PermissionGrant -All |
    Where-Object { $_.ResourceId -eq $graph.Id -and ($_.Scope -split " ") -contains "Calendars.Read" } |
    Select-Object ClientId, ConsentType, PrincipalId

Other Calendars permissions

Check every app in your tenant → Permission explainer

Sources