When you choose the files you want to transfer, it gives you a 6 digit code or a QR code. Once you enter that, the files are transferred! It's available for most all major platforms, but isn't open source. [3]
I haven't read their privacy policy. Frankly, I'd rather not know...
[1] https://send-anywhere.com/
[2] https://support.send-anywhere.com/hc/en-us/articles/11500385...
[3] https://support.send-anywhere.com/hc/en-us/articles/11500388...