Connecting a registrant to a participant from meeting joined/left webhooks

We have an event registration service that we want to integrate with Zoom to do the following with both Zoom meetings and webinars.

  1. Allow users placing orders to have their registrations associated with a unique registrant in Zoom
  2. When a user clicks the Zoom join URL to join the Zoom meeting/webinar, we want to receive a notification from Zoom that the registrant has joined the meeting
  3. When a user leaves the Zoom meeting/webinar, we want to receive a notification from Zoom that the registrant has left the meeting

Where we’re most confused currently is the API documentation regarding the registration_id and the participant_id when we receive webhook events from Zoom. For instance, if our system receives a unique registrant_id for each registrant, we’re unable to find a way to associate that registrant_id with the webhook event that is sent from Zoom because…the webhook doesn’t include the registrant_id.

It seems like we’re missing something really simple, since it feels like knowing who registered and then matching that with who joined/left a meeting/webinar would be pretty common.

Any chance someone can help us in understanding how we can connect the registrant_id to the participant_id in the participant joined meeting webhook?

Hey @cozimek

Thanks for posting on the Zoom Devforum! I am still learning, but I will try my best to help answer your question. :slightly_smiling_face:

Checkout this related thread that may have the answer you are looking for:

If this thread did not help, please let us know by replying back here and someone from the Developer Relations team will get back to you shortly.


The bot response doesn’t seem to answer my question.

Hey @cozimek,

Here is the relationship between a registrant and a participant:

Let me know if that helps! :slight_smile:


@tommy thanks so much! A quick follow-up to start: why would we receive a blank value for the meeting.participant_joined webhook, but a non-null value for the ```
meeting.participant_left webook?


@tommy as a secondary follow-up, we’ve just confirmed that if someone joins a meeting, and is logged into Zoom when they join, participant:id value is null in the webhook. Why would this happen?

Hey @cozimek,

Thanks for raising these follow ups with us—as a next step, can I ask that you email the following to

  • meeting IDs,
  • webhook payloads,
  • link to this forum post,
  • and the scenarios you’re referencing

This will help us to take a closer look at your account/use cases, specifically.


@will.zoom on it, thanks!


Thanks @cozimek! :slight_smile:


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