How does a CORS unblocker work from client side?

As far as I know, websites that don’t have Access-Control-Allow-Origin cannot be fetched using XMLHTTPRequest from client side so this problem can be solved only from server side by adding * to Access-Control-Allow-Origin in the header section.

let url = 'https://tv.jordkris.com';
fetch(url).then(res => res.text())
.then((text) => {
  var parser = new DOMParser();
  var html = parser.parseFromString(text, "text/html");
  var target = document.getElementById('target');
  target.innerHTML = text;
})
.catch(err => console.error(err.message));
<div id="target"></div>

However, recently I came across a website that can perform CORS unblocking of a URL.

let url = 'https://corsproxy.io/?' + encodeURIComponent('https://tv.jordkris.com');
fetch(url).then(res => res.text())
.then((text) => {
  var parser = new DOMParser();
  var html = parser.parseFromString(text, "text/html");
  var target = document.getElementById('target');
  target.innerHTML = text;
})
.catch(err => console.error(err.message));
<div id="target"></div>

How does the website work so that it can unblock CORS from the client side?