A little bit about debugProxy
debugProxy is a HTTP/S hosted proxy server that lets you interact with the traffic passing through it, using a web based dashboard.
This means, for example, you can use the browser on your desktop or tablet to view the traffic being sent from apps on your mobile phone to the Internet.
debugProxy can intercept HTTPS and HTTP2 traffic by acting as a Certificate Authority and issuing certificates on-the-fly.
For a quick demostration there are some videos. Below is a is a screen shot of the web dashboard.
It's free to register and start a proxy server.
HTTP proxy requests are very similar to regular HTTP requests. They are still common in large companies and Universities. Many devices, operating systems and applications support using them.
View & modify traffic
The web dashboard shows the requests, responses and headers being sent through the proxy as they happen. It is also possible to pause requests and modify them before they are sent and before they are returned.
Viewing and modifying HTTPS traffic is possible by issuing certificates on the fly. The certificates are issued by a root certificate that must be trusted by the client.