How can I delete my webinar video?
There's option to Delete your event video, if you want to? Your video library has no use limit or size requirements affecting webinar events.
Its not a typical action, though you may want to in order to keep your Library in order, A Switch Video operation is much more common to replace video at a Webinar Event,
Check the link > HERE < to Switch a Video.
To Delete go to "My Library" from top menu bar or > HERE < and beside the webinar video name, click on the "Delete" link.
Please be aware, once you delete your video, it cannot be restored.

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What encoding do you do to the video?
Can I change my webinar video without starting a new event? (switch video)