It pretty much feels like the file is just uploaded and a link (string) is generated to communicate that over sound. The receiving browser then just uses that "download link" to download the actual file. The file uri also just downloads a file from their servers.
Just saying, as it's not really mentioned on the site as far as i can see.
-REST
-GET, POST, PUT
-JSON
-Javascript
-MQTT
And all that helped me a lot in my career, just because i wanted to automate a few things. And now Node-RED is just irreplaceable in my private life.