Load markup from another site via cors ajax?

Question

JavaScript

How to download markup from another site through a browser script? For example, I need to get certain meta tags from yandex.ru.

The article https://developer.mozilla.org/ru/docs/Web/HTTP/CORS says that there are "simple" requests, if I use GET and do not use non-standard headers, then everything should work.
Here is the code:

fetch('https://bootstrap-vue.js.org')
    .then(res => res.text())
    .then(res => {
        console.log(res)
    })
    .catch(err => console.log(err))

It works, but not on all sites, for example, on https://bootstrap-vue.js.org it works, but if I turn to Yandex, then the error

I tried to add different headers, I tried to use different modes for fetch, but it didn’t work out.

Answer 1

fetch is also ajax, not a simple GET.
Or set up that other server, or use your own proxy (you can even cache ☝), or refuse ajax.

Answer 2

For simple ones to work, there must be alow origin from the origin from which you make the request or from *.