first i have to apologize, my english is not good, that's how google translated it. Maybe that's why I didn't find the answer

With the current JCE I enter the following code in the editor

<p class="responsive-video">
<iframe src="https://www.joomlacontenteditor.net/www.youtube.com/embed/cXiCJUNwIz8" width="640" height="360" frameborder="0" allowfullscreen="allowfullscreen"></iframe>

When I switch from code to editor, it changes the code even when it's saved. red_different

<p class="responsive-video">
<iframe src="https://www.joomlacontenteditor.net/www.youtube.com/embed/cXiCJUNwIz8" width="640" height="360" style="width: 640px; height: 360px;" frameborder="0" allowfullscreen="allowfullscreen" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"></iframe>
</p>

insite template i use this code

.responsive-video {
position:relative;
padding-bottom:56.25%;
padding-top:15px;
height:0;
overflow:hidden;
}
.responsive-video iframe {
position:absolute;
top:0;
left:0;
width:100%;
height:100%;
}

in the TinyMCE editor it works even if I switch the code sector on or off.
I've been using this code for a long time, no problems so far.

Greetings

Dear Ryan

Thank you so much for the help. This works again with 2.0.29 RC.
It converts old code from to exactly new code from you and I don't even have to replace the old ones, they are automatically adjusted and continue to work.

Great, but with your code the message comes up:
Not Found The requested URL /http://www.youtube.com/embed/cXiCJUNwIz8 was not found on this server

But without /http: it works.

I mentioned the problem interestingly on my website,
https://www.cms-joomla.ch/index.php/inhalte-erstellen/video-responsive-schalten
because others had some problems too, but on your side (I've been using the pro for a long time) the 2.9.29 isn't official yet, still 2.9.28. Should I refrain from giving a hint until that is the case?

Greetings from a hobby jooma fan with several pages from Switzerland.

Beat (is a man first name in german not english meanig beat 🙂 ) Feser www.feser.ch

Thank you again.

I didn't mean anything bad about the HTTP, no criticism, sorry. That's just how automation works. I could have come up with the idea myself, but at least I noticed it.
;)
Everything is ok, if you have time and unlock it, I'll be happy to enter it on my website, many will probably be happy.

Greetings Beat Feser

Thanks again.
I didn't mean the HTTP badly, no criticism, sorry. This is how automation works. I could have come up with the idea myself, but at least I noticed it.
;)
Everything ok, if you have time and activate it, I'll be happy to enter it on my website, many will certainly be happy.

Kind regards, Beat Feser

Dear Ryan
I was test it on my site and I am happy, it's work well, it chage all old code automaticly.
great work thanks again.
B. Feser