Examine source code of InstaZipper

{
  "name": "InstaZipper",
  "description": "A tool to download an archive of your images on Instagram",
  "version": "1.0",
  "manifest_version": 2,
  "permissions": [
    "*://instagram.com/*",
    "*://*/*",
    "activeTab",
    "webRequest"
  ],
  "browser_action": {
    "default_icon": {
      "16": "/icons/16.png",
      "32": "/icons/32.png",
      "48": "/icons/48.png",
      "128": "/icons/128.png",
      "512": "/icons/512.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "css": [
        "output.css"
      ],
      "matches": [
        "https://*.instagram.com/*"
      ]
    }
  ],
  "icons": {
    "16": "/icons/16.png",
    "32": "/icons/32.png",
    "48": "/icons/48.png",
    "128": "/icons/128.png",
    "512": "/icons/512.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{08ddfeae-bc3d-4258-a546-8ffea1d4e463}"
    }
  }
}