cdnjs is a free distributed JS library delivery service.
Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
Howler.js is an audio library with support for the Web Audio API and a fallback mechanism for HTML5 Audio.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.
Unpkg is a content delivery network for everything on npm.