YouTube video width

I am building a new website layout. I have embed a lot of YouTube video by pasting only the YouTube video URL in a blogpost. For example https://www.youtube.com/watch?v=CojrNhybeg0.

On a desktop screen works it fine. But it’s not responsive on the tablet and mobile screens. Is there any way to get it responsive on the tablet and mobile screens?

I have already tried to follow this guide https://avexdesigns.com/responsive-youtube-embed/, but it doesn’t work.