embed video set max width

It depends.
If you talk about Jetpack, I don’t know.

But if you use auto-embed supported by WordPress (Youtube etc…)
You can define the width limit here
https://www.your-site.com/wp-admin/options-media.php

Perhaps it can help.

hello, page doesn’t exist.
I set the options for max size in media (auto embed).
I think is not possible to set sizes for various pages (the width size of my blog changes).