Random invidious redirect (fetches list from api.invidious.io, attempts to keep 100% healthy ones, picks random instance from the list; tested with violentmonkey, greasemonkey (firefox) and tampermonkey (brave)

invidious-redirect.userscript.js

// ==UserScript==
// @description Redirects Youtube URLs to Invidio.us
// @name Invidious Redirect
// @namespace Backend
// @downloadURL https://gist.githubusercontent.com/m0n5t3r/b7c13265152bd8c997f2d22afb4932e7/raw/invidious-redirect.userscript.js
// @include http://www.youtube.com/*
// @include https://www.youtube.com/*
// @include https://consent.youtube.com/*
// @version 1.6
// @run-at document-start
// @grant none
// ==/UserScript==

// prevent youtube content from loading; used to be a simple document.write, but 
// * at first, greasemonkey complained
// * then google started redirecting everything to consent.youtube.com, which has CSP that requires trusted types
var newDoc = document.implementation.createHTMLDocument (""),
    h1 = document.createElement("h1");

h1.innerText = "Redirecting, please wait...";
newDoc.body.appendChild(h1);

document.replaceChild (document.importNode(newDoc.documentElement, true), document.documentElement);
document.close();

const blacklist = [
    "invidious.xyz",
    "invidious.site",
    "invidiou.site",
    "invidious.reallyancient.tech",
];

function find_parameter(name) {
    var result = null,
        tmp = [];
    location.search
        .substr(1)
        .split("&")
        .forEach((item) => {
          tmp = item.split("=");
          if (tmp[0] === name) result = decodeURIComponent(tmp[1]);
        });
    return result;
}

// pick a random instance with a good health record
fetch("https://api.invidious.io/instances.json?sort_by=type,health").then((response) => {
    response.json().then((instances) => {
        var filtered, domain, idx, a;

        filtered = instances.filter((i) => {
            var monitor = i[1].monitor;
            var type = i[1].type;

            if(type != "https") {
              return false;
            }

            if(blacklist.includes(i[0])) {
                return false;
            }

            if (monitor) {
              return monitor.dailyRatios[0].ratio == "100.00";
            }

            // no monitoring data, let it through; might change later to filter in 2 steps and only
            // let unknown status instances through if no health info has been found
            return true;
        }).map((i) => { return i[0] });

        idx = Math.floor(Math.random() * filtered.length);
        domain = filtered[idx];

        if (/watch\?|channel|embed|shorts/.test(window.location.href) && window.location.href.indexOf('list=WL') < 0) {
            a = window.location.href.replace(/www\.youtube\.com/, domain).replace('/shorts/', '/watch?v=');
            window.location.replace(a);
        }

        // youtu.be and youtube.com seem to force-redirect to the consent thing lately, handle it here
        if(/consent\.youtube\.com/.test(window.location.href)) {
            a = find_parameter('continue').replace(/www.youtube.com/, domain).replace('/shorts/', '/watch?v=');
            window.location.replace(a);
        }
    });
});

New PSA from Invidious project:

"invidio.us is now deprecated, invidious.io is the new domain.

The invidious-redirect website ( invidio.us ) is now https://redirect.invidious.io/

The instance API ( instances.invidio.us ) is now https://api.invidious.io/

The uptimerobot page ( uptime.invidio.us ) is now https://uptime.invidious.io/

https://git.invidious.io/ redirects to the Github page of the project: https://github.com/iv-org/invidious/

https://docs.invidious.io/ redirects to the documentation website of the project: https://github.com/iv-org/documentation/

https://invidious.io/ will become in the future a "project presentation" page (like https://searx.me/ ), we will use a markdown framework like Hugo.

Projects using something from invidio.us need to move to the new domain."

updated, thanks for letting me know

You're welcome!