Beginners TamperMonkey 2024 | Add Custom JavaScript to YouTube.com

Hands-on tutorial for beginners on how to use Tampermonkey plugin (Greasemonkey add-on) in Firefox (works in Chrome too) to modify a YouTube website with a custom Javascript script (code). Updated tutorial in 2024. How to get started with TamperMonkey.

How to change a website with your own code? A beginners lesson about practical Greasemonkey scripts.

In this tutorial, I will show you how to inspect the YouTube source code to alter it with JavaScript code injected using a Tampermonkey app / plugin / add-on. This method works on both Firefox and Chrome. You can learn from it as a follow along tutorial to then implement your own scripts altering the webpages of your choice. Such Tampermonkey scripts are useful for displaying additional data / information or for autocompletion of forms to speed up your workflows.