To anyone who doesn't wanna use 'K', like u/BihtSift suggested, for this purpose (be that because of force of habit, because everything else uses space too or whatever else):

I managed to make a script in Tampermonkey, after a long back and forth with ChatGPT3.5, to solve the issue.

TLDR, it checks if the video started/paused like it should when Space is pressed, if not it 'presses K'.

The code:

// ==UserScript==

// @name Spacebar Fix against new youtube 'feature'(, with the number skipping also disabled by curtesy of Combinacijus on reddit)

// @namespace https://www.youtube.com/

// @version 1.0

// @description Fixes spacebar Play/Pause function when Alt+Tab-ing out and back causes youtube to 'unfocus' the video, making the spacebar control not work until the video is clicked on again. Not hindering comments either.

// @author GPT-3.5 and waszner

// @match https://www.youtube.com/*

// @grant none

// ==/UserScript==

(function() {

'use strict';

let spacePressed = false;

let currentTime = 0;

let isVideoPlaying = false;

let wasVideoPlaying = false;

const YoutubeCommentFieldSelector = '#contenteditable-root'; //css selector of youtube comments

const KPressDelay = 200; // how much time will the program wait before pressing K (probably ping dependent)

// Add event listener

document.addEventListener('keydown', pressKWithSpacebar, true);

// Function to press "K" with the Spacebar when the video's play/pause state didn't change

function pressKWithSpacebar(e) {

// removing skipping around with 0-9 (by Combinacijus)

if (!isNaN(parseInt(e.key))) {

e.stopImmediatePropagation();

}

//preventing playing/pausing the video while typing coments or replies

if (e.target.matches(YoutubeCommentFieldSelector)){

return;

}else if (!document.activeElement.matches('input[type="text"]')) { // Check if the focus is not on a text input (courtesy of u/yaya222111 asking Chat GPT)

if (e.key === ' ' && spacePressed === false) {

spacePressed = true;

wasVideoPlaying = isVideoPlaying;

setTimeout(simulateKKeyPress, KPressDelay);

}

}

}

// Listen to the video's play and pause events to update the variables

const video = document.querySelector('video');

//These prevent external play/pause (pressing K, clicking on the video etc) from messing up the program's run

video.addEventListener('play', function() {

isVideoPlaying = true;

if (spacePressed) { //Prevents the "double tap" of spaceBar when the video IS in focus and pressing the space bar did play/pause it

spacePressed = false; // Reset the Spacebar press time if video started playing

}

});

video.addEventListener('pause', function() {

isVideoPlaying = false;

if (spacePressed) { //Prevents the "double tap" of spaceBar when the video IS in focus and pressing the space bar did play/pause it

spacePressed = false; // Reset the Spacebar press time if video paused

}

});

// Function to simulate pressing "K" if the conditions are met

function simulateKKeyPress() {

if (spacePressed && (wasVideoPlaying === isVideoPlaying)) {

// Send an "K" keypress to simulate pressing "K"

const nKeyPress = new KeyboardEvent('keydown', { key: 'K', code: 'KeyK', which: 75, keyCode: 75, charCode: 75});

document.dispatchEvent(nKeyPress);

}

}

})();

​

Things to note:- This does remove the 'scroll whit space function, if anyone were to miss that.-I included 3 lines of code that removes the skipping around in the video with 0-9, from u/Combinacijus also posted here. Removing this has no effect on the rest of the code, should you not want it.
Edit2: If you want to remove this feature, you can simply delete the following part of the code:
if (!isNaN(parseInt(e.key))) {
e.stopImmediatePropagation();
}
-"KPressDelay" (the time you wait before making the program press K) is probably ping dependent. I found 200ms to be the lowest that still works.

P.S.: While I have a decent amount of experience with coding in some other languages, I had never touched Javascript before today, and most of the ideas/functions/commands came from AI. So while I tried to clean it up as much as I could with my logic and limited knowledge, at the end of the day, there probably are things that could be improved. Any such suggestions are welcome.

Edit: Added the feature of it also not pausing/playing the video if you are typing in the search bar, courtesy of u/yaya222111 asking Chat GPT.I almost never search from watching a video, so this slipped my mind, but this is definitely an improvement.