HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
reCAPTCHA is a free service from Google that helps protect websites from spam and abuse.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.
ShareThis provides free engagement and growth tools (e.g., share buttons, follow buttons, and reaction buttons) for site owners.
Unpkg is a content delivery network for everything on npm.