Darkmode.js is a JavaScript library that enables an HTML element to switch between CSS themes.
JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.
Open Graph is a protocol that is used to integrate any web page into the social graph.
OpenResty is a web platform based on nginx which can run Lua scripts using its LuaJIT engine.
Typekit is an online service which offers a subscription library of fonts.