Apple Sign-in is based on OAuth 2.0 and OpenID Connect, and provides a privacy-friendly way for users to sign in to websites and apps.
Calendly is an app for scheduling appointments, meetings, and events.
cdnjs is a free distributed JS library delivery service.
Facebook pixel is an analytics tool that allows you to measure the effectiveness of your advertising.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.