According to this: https://codex.wordpress.org/Embeds
You can just paste in your YouTube link into your post body and it becomes an embedded YouTube Video. This works for me, but it seems to ignore any parameters I pass the YouTube link. For example, if I paste in:
The generated HTML is:
<iframe width="500" height="281" src="https://www.youtube.com/embed/XYZ12345?feature=oembed" frameborder="0" allowfullscreen=""></iframe>
As you can see, the
&rel=0 parameter is missing from the generated embed html. Is there a trick to passing parameters to the embed?