This site was very helpful when I refractored a program from using libcurl to cpprest. I used it to make sure the sent http request headers where exactly the same.
You could have just looked at the traffic directly with wireshark rather than trust an external site.
I think this might not be possible for SSL/TLS traffic, without some kind of MITM.
It is possible with SSL/TLS traffice: you need to supply private key to WireShark, so it will be able to decode conversation.
Most dev 'MITM' proxy tools have a way to inspect HTTPS by creating a new key and adding it to your systems trust.
Charles has a fairly neat way of making it all work.
I'll remember that next time. I been using fiddler to see websites http traffic which is helpful. But my programs http traffic doesn't show up there.. So ill try wireshark next time.