YouTube: How to present embed video with sound muted
Updated Add &mute=1 to the end of your url. Your new code would be: Expand snippet
Updated Add &mute=1 to the end of your url. Your new code would be: Expand snippet
I believe this is an issue with the target origin being https. I suspect it is because your iFrame url is using http instead of https. Try changing the url of the file you are trying to embed to be https. For instance: to be:
As of September 25, 2018, you are not be able to disable related videos. Instead, if the rel parameter is set to 0, related videos will come from the same channel as the video that was just played. YouTube API