HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
LazySizes unveilhooks plugin extends lazySizes to lazyload scripts/widgets, background images, styles and video/audio elements.
Modernizr is a JavaScript library that detects the features available in a user's browser.
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.