Wappalyzer

This is a browser extension that hooks and uncovers the underlying technologies that a website is built on. For example, it can detect CMS (content management systems) such as Drupal, WordPress, and Joomlaa. It also detects eCommerce platforms (eg. Magneto or Shopify), web servers (eg. Nginx or Apache Tomcat), JavaScript frameworks (eg. React or Jquery ), analytical tools (eg. Google Analytics or comScore), and many other technologies. This can be very useful to get a quick glimpse into what technologies your target is running. While nothing is 100% accurate, it is a good idea to always double-check and verify results, but having this initial information is very useful.