Examine source code of Open SEO Stats

{
  "manifest_version": 2,
  "name": "Open SEO Stats",
  "version": "1.3",
  "description": "Analyze on-page SEO stats of any website including title, meta tags, headings, links, canonical, and more.",
  "permissions": [
    "tabs",
    "activeTab",
    "downloads",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Open SEO Stats"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "contentScript.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1d110e4a-52b1-49e1-acef-f2064d5b5fc8}"
    }
  }
}