Extended Properties Missing from Attendee Calendar Events in Microsoft Graph

Question

Hello Microsoft Graph Support,

I’m encountering an issue with the singleValueExtendedProperties on calendar events:

• When I set extended properties on a meeting event (e.g., custom metadata such as myUniqueGuidId) on the organizer’s calendar, I can successfully retrieve these properties via the Microsoft Graph API on the organizer’s event.

However, when querying the attendee’s calendar events, the same extended properties are not present on the attendee’s copy of the meeting, even though the meeting itself appears on their calendar (e.g., visible in Teams and Outlook).

This causes issues for my application, which relies on these extended properties to identify and filter meetings by custom metadata on both organizer and attendee sides.

Expected behavior: I expect the extended properties set on the organizer’s event to be replicated or accessible on the attendee’s copy of the event so that attendees’ calendars contain the same metadata.

Actual behavior: Extended properties appear only on the organizer’s event copy, not on attendees’ copies.

Graph Explorer request sample which returns result for organizer but not for attendees even though the event appears on both organizer and attendee Outlook and Teams calendars:
https://graph.microsoft.com/v1.0/me/events?$top=50&$select=id,subject,start,end,organizer,attendees,onlineMeeting,singleValueExtendedProperties&$expand=singleValueExtendedProperties($filter=id eq 'String {guid} Name myUniqueGuid')&$filter=singleValueExtendedProperties/Any(p: p/id eq 'String {guid} Name myUniqueGuid' and p/value eq 'value')

Could you please clarify if there is any supported way to propagate these extended properties to attendee event copies? If not, is there any recommended approach or best practice for handling custom metadata on attendee calendars?

Thank you!

Answer 1

Hi Mohammad Ghabin (ASAL Technologies Ltd)

Thanks for reaching out on Microsoft Q&A!

You're encountering a known behavior of the Microsoft Graph API. Extended properties (like singleValueExtendedProperties) are not automatically propagated from the organizer's event to the attendees' copies of the event. Each attendee receives their own copy of the event, and these copies do not inherit custom metadata unless explicitly set. This is by design.

So, what you can do is retrieve all extended properties from the "master" copy (organizer) and write them to the attendees' events. Please find the link to the Graph documentation below:

https://learn.microsoft.com/en-us/graph/api/resources/extended-properties-overview?view=graph-rest-1.0

Please click ‘Accept answer’ if you think my answer is helpful. Feel free to drop additional queries in the comments below!

Kind regards,

Sonny