UserScript to force 1080p60 (Source) video quality on Twitch

script.js

// ==UserScript==
// @name         Force 1080p60 (Source) video quality on Twitch
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        *://*.twitch.tv/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// @author       Antoine Delia
// ==/UserScript==

var desiredQuality = "1080p60 (Source)"

(function() {
    'use strict';

    var nothing = setInterval(function() {
        var settingsButton = document.querySelectorAll('[data-a-target="player-settings-button"]')[0];
        if (settingsButton == null) {
            return
        }
        settingsButton.click();

        var divs = document.getElementsByTagName("div");
        var searchTextQuality = "Quality";
        var qualityFound;

        for (var i = 0; i < divs.length; i++) {
            if (divs[i].textContent == searchTextQuality) {
                qualityFound = divs[i];
                qualityFound.click();

                var searchTextSource = desiredQuality;
                var sourceFound;

                for (var j = 0; j < divs.length; j++) {
                    if (divs[i].textContent == searchTextSource) {
                        sourceFound = divs[i];
                        sourceFound.click();
                        break;
                    }
                }
                break;
            }
        }

        settingsButton.click();
    }, 10000);

})();

userscript_1080p_twitch.md

UserScript to force 1080p Quality on Twitch

You need to install this in the TamperMonkey extension.

This might break if your default language for Twitch is not English.

You can also change the desired quality by updating the desiredQuality variable.