cdnjs is a free distributed JS library delivery service.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Next.js is a React framework for developing single page Javascript applications.
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.
Unpkg is a content delivery network for everything on npm.
Vercel is a cloud platform for static frontends and serverless functions.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.