Restricted Mode: On

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Restricted Mode: On",
  "description": "Automatically enables restricted mode on Youtube.",
  "version": "0.0.1",
  "icons": {
    "16": "icons/16.png",
    "48": "icons/48.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "author": "Daniel Kladnik @ kiboke studio",
  "permissions": [
    "notifications"
  ],
  "background": {
    "scripts": [
      "data/main.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "run_at": "document_start",
      "css": [
        "data/youtube.css"
      ],
      "js": [
        "data/youtube.js"
      ]
    }
  ]
}