cdnjs is a free distributed JS library delivery service.
Google Analytics is a free web analytics service that tracks and reports website traffic.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.
React is an open-source JavaScript library for building user interfaces or UI components.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.