Examine source code of Passphrase Meter

{
  "manifest_version": 2,
  "name": "Passphrase Meter",
  "version": "2.4",
  "description": "Check your passwords and passphrases for strength without any network access. See the estimated entropy, a clear rating, how long an offline attack might take, and tips to make it tougher — all computed locally.",
  "icons": {
    "32": "assets/icon-32.png",
    "48": "assets/icon-48.png",
    "64": "assets/icon-64.png",
    "96": "assets/icon-96.png",
    "128": "assets/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{26aff512-be1c-406f-8a9c-9b172ddeb670}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [],
  "browser_action": {
    "default_title": "Passphrase Meter",
    "default_popup": "app/popup.html",
    "default_icon": {
      "32": "assets/icon-32.png",
      "48": "assets/icon-48.png",
      "64": "assets/icon-64.png"
    }
  }
}