Examine source code of Crypto Ticker

{
  "manifest_version": 2,
  "name": "Crypto Ticker",
  "description": "Shows the current price of your favourite crypto currency in the browser toolbar. You can select between > 1,500 cryptos.",
  "icons": {
    "16": "skin/ticker_16.png",
    "32": "skin/ticker_32.png",
    "48": "skin/ticker_48.png",
    "128": "skin/ticker_128.png"
  },
  "version": "1.0.18",
  "author": "Crypton",
  "browser_action": {
    "default_icon": {
      "16": "skin/ticker_16.png",
      "32": "skin/ticker_32.png",
      "48": "skin/ticker_48.png",
      "128": "skin/ticker_128.png"
    },
    "default_title": "Crypto Ticker",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "js/rate.js",
      "js/background.js"
    ]
  },
  "permissions": [
    "https://api.coincap.io/",
    "https://www.ecb.europa.eu/",
    "storage"
  ]
}