Disable caching of attached css/js libraries for custom module? I have been trying to disable caching during development so I followed drupals guide step by step: https://www.drupal.org/node/2598914

After doing this I would assume that the caching is completely disabled but when I am loading a js/css file for a specific module in mymodule/mymodule.libraries.yml I still have to clear all caches for me to see any updates.

How do you disable caching for attached libraries in custom modules?  

test_module.routing.yml

test_module.test:
  path: '/test-me'
  defaults:
    _title: 'Testing module css cache'
    _controller: 'Drupal\test_module\Controller\TestController::test'
  requirements:
    _permission: 'TRUE'


test_module.libraries.yml

test:
  version: VERSION
  css:
    theme:
      test.css: {}


TestController.php

&lt;?php

namespace Drupal\test_module\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Render\Markup;

class TestController extends ControllerBase
{
    public function test()
    {
        return [
            "#markup" =&gt; Markup::create("&lt;div class='test-class'&gt;Hello World&lt;/div&gt;"),
            '#attached' =&gt; [
                'library' =&gt; ['test_module/test']
            ]
        ];
    }
}


test.css

.test-class {
    padding: 40px;
    background-color: blue;
}


If I change the background-color to red for example, and refresh the page (F5, Ctrl+F5, Ctrl+Shift+R, Right click refresh -> Clear cache and Hard Rest), it will not change to red until I clear all caches.

What piece am I missing to make this work? Or is it just not possible?

Note: It doesn't matter if I clear my browser cache at all (I currently have it disabled with devtools open)
You are on the wrong track. Caching of static assets (and CSS files are static assets when you disable CSS/JS aggregation) has nothing to do with Drupal's cache. Disable the caching of *.js and *.css files on your web server instead (e.g in .htaccess if you are using Apache).