- USB connection? I don't want to dig out my cable and climb under the desk to plugin the USB cable.
- Samba share? Forget it.
- FTP server app? Works, but usually quite slow and painful.
- Start a HTTP server to serve the directory? That works, but seriously?
- Sending via E-Mail or Dropbox? Oh FFS, both devices are connected to the same WiFi access point, how can it be that uploading the file to a cloud hosted across the world and downloading it again from my other device is the simplest approach?
So far, Sharedrop is the simplest solution I know that works across any device that has a modern browser and that allows me to send the file directly from one computer to the other, without the need for logins or accounts or external software or arcane command-line incantations.
(The WebRTC Datachannel stack is horrible and mostly neglected by browser vendors, especially Google, but that's another story...)
Of course of you're using the Apple ecosystem, there's AirDrop...
It uses local network when available and of course internet when not. It also does iOS.. if only more apps were supporting FileProvider functionalities, so you don't have to import-duplicate all the synced data first.
Also single file sharing seems interesting, but this is not what you usually do on daily basis... You just want to drop some file to shared folder most of the time, or to have a ton of different files synced automatically.
I did this all the time between my computer and my brother's computer as a kid. They were on the same network (dad had the whole house wired for ethernet when they gut rehabbed it) and we just used Windows file explorer to drag and drop files from one computer to the other.
Also check Syncthing. They have a very nice interface that skips the cloud...