When writing How to remove event listener on Youtube player?, I tried to create a Stack Snippet but I could not add the YouTube API client, which was needed to display the issue.
The client is on https://www.youtube.com/iframe_api which does not include a
.js extension and Stack Overflow adds an external library, which refuses to include the script. In lieu of a
.js extension, it might work to test the mime-type of the URL.
There might be other sandbox issue around embedding a YouTube video on Stack Overflow but this was the first that stopped me.