How to make smooth scrolling of the entire site, without twitching?

Question

Video

Hello! I saw these previews at one studio: Video
I want to know how it's easier to implement? Maybe there are some services or automated plugins?
Scrolling with the mouse - it turns out twitchy. Arrow down - also jerky. I tried to put all sorts of plug-ins on the browser that make a smooth scroll - it still jerks in places.

Answer 1

try to add in css

html  {
  scroll-behavior: smooth;
}

and just jquery

$("html, body").animate({ scrollTop: $(document).height() }, 25000);

seems to be more or less normal

Answer 2

Add to CSS

html  {
  scroll-behavior: smooth;
}

And make buttons on the side of the page (or somewhere else) that, with a slight pause, will scroll the page by several tens of pixels, you can program it through JS