Examine source code of Unique Domain Extractor

{
  "manifest_version": 2,
  "name": "Unique Domain Extractor",
  "version": "1.0",
  "description": "Extract all unique domains from links on the page.",
  "browser_action": {
    "default_icon": {
      "64": "icon64.png",
      "128": "icon128.png"
    },
    "default_popup": "popup.html",
    "default_title": "Extract Domains"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{722e7e77-61e8-4c9e-b2da-6cb0e475d8dc}",
      "strict_min_version": "116.0"
    }
  }
}