If you ever land on a site and wonder how it was built, then you might find these Chrome extensions useful. This article will compare the two most prominent options.
Library Detector — found nothing. Library Sniffer — found SPDY, GitHub.
cnn.com
Library detector mentions jQuery twice, and core-js is a huge amount of text for some reason. jQuery 1.12.3, jQuery (Fast path), React, Modernizr 3.6.0, Moment.js 2.29.1, core-js.
reddit.com
It is pretty interesting to see that reddit uses Varnish and react.