manifest_v3.json

{
  "manifest_version": 3,
  "name": "YouTubeLegacyUI",
  "version": "1.0.0",
  "description": "YouTubeを旧UIにします",
  "icons": {
    "16": "icons/icon_x16.png",
    "48": "icons/icon_x48.png",
    "128": "icons/icon_x128.png"
  },
  "content_scripts": [
    {
      "matches": ["*://*.youtube.com/*"],
      "css": ["css/main.css"]
    }
  ]
}