Youtubespeed

Youtubespeed.user.js

  // ==UserScript==
// @name        Youtubespeed
// @namespace   Youtubespeed
// @include     https://www.youtube.com/*
// @version     1
// ==/UserScript==

var playspeed = 0.25, //---> set the speed you want here (replace "3.5", don't remove the comma behind it)
    prevspeed = 0,
    rprevspeed = 0,
    curspeed = 0,
    curtime = 0,
    sdif = 0,
    bleh = 0;
setInterval(function(){
    try {
        curspeed = Math.round(10 * document.getElementsByClassName('html5-main-video')[0].playbackRate) / 10;
        curtime = 0;
        try {curtime = document.getElementById("movie_player").getCurrentTime();}
        catch(err) {}
        if (prevspeed === 0){
            rprevspeed = 1;
        } else {
            rprevspeed = prevspeed;
        }
        if(curspeed != prevspeed){
            sdif = Math.round(10 * (curspeed - prevspeed)) / 10;
            if (sdif > 0){sdif = "+" + sdif;}
            console.log("Speed changed to " + curspeed + " (previously it was " + prevspeed + "). " + sdif);
        }
        if (curspeed == 1 && rprevspeed > 1.01 && curtime < 3){
            document.getElementsByClassName('html5-main-video')[0].playbackRate = rprevspeed;
        } else if (curspeed == 1 && curtime < 3){
            document.getElementsByClassName('html5-main-video')[0].playbackRate = playspeed;
        } else if (curspeed == 4){
            document.getElementsByClassName('html5-main-video')[0].playbackRate = 3.999;
        }
        prevspeed = curspeed;
    }
    catch(err) {}
}, 100);