This is from Google Productforums
To be sure. Yes, you can embed private videos. However, this is really impossible to do because private YouTube videos require the viewer to have a YouTube account, sign up for this account, and add this account to the video access list. They are limited to 50 people. You can embed videos that are not on the list; they do not have the same authentication restrictions as private videos. However, all that is needed is to view the video in the list to find out the URL. If your site is crawled by search engines, this may be publicly available.
You may want to watch your own videos for better control and make sure you are not violating the YouTube Terms of Use (which prohibits the use of the built-in player).
Vimeo.com also has more robust access controls and can only allow embedding videos in a specific domain. However, they do not allow commercial use ... so this may be a trick if this applies to you.
hjpotter92
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