KEIBIDROP and croc

A transfer tool, and a folder you can browse.

By Marius-Florin Cristian · 2 September 2026

croc sends what you name, from the command line, with a fresh code phrase each time. KEIBIDROP keeps saved peers so there is no code to pass along, it has a GUI as well as a CLI, and it can mount the other machine's folder so you pull one file out of it.

Side by side

	KEIBIDROP	croc
Interface	GUI and CLI	CLI and a browser page
Per-transfer code	No, saved peers	Yes, a code phrase each time
Browse the other side	Yes, it mounts	No
Open a file without receiving the folder	Yes	No
Account	None	None
File bytes through a public relay	Only through the bridge, when direct fails	Yes, unless both machines are on one local network
Resume after a drop	Per chunk	Yes
Encryption	End to end, X25519 with ML-KEM-1024	End to end, PAKE
Source code	Open, AGPL-3.0	Open, MIT
Install footprint	Installer, plus a driver to mount	One binary

Saved peers instead of a code each time

The two sides exchange an 86 character fingerprint once and connect on it afterwards, so a folder you use every week costs nothing to reopen. croc generates a fresh code phrase per transfer and someone has to carry it across.

The relay's role

During pairing each side leaves an encrypted note on the relay and fetches the other side's note. No file bytes pass through it: they go direct when the two machines can reach each other, and through the bridge when they cannot. On one local network the peers find each other by a multicast announcement and the relay is not involved. A session that is already open keeps running if the relay goes down. croc's public relay forwards the encrypted bytes unless both machines are on one local network, so a transfer across networks stops when the relay does. The paths are described in Network paths.

Browse the other side and pull one file

KEIBIDROP mounts the other machine's folder as a folder on yours, and a read pulls only the bytes it touches, so you open the one file you came for instead of receiving a whole directory. It is a real filesystem, so Premiere, Resolve, Blender, grep and git open a path on it the way they open a local one.

Post-quantum key exchange

KEIBIDROP is AGPL-3.0, so anyone can confirm the key exchange is X25519 with ML-KEM-1024, and a recording taken today has to break both halves to be read once quantum hardware exists.

Limits

Platforms. Windows, macOS, Linux and Android today, and iOS is next.
Sending needs no driver. A whole file transfers with nothing extra installed. Add WinFsp, fuse3 or macFUSE on the machine that mounts, and the same folder opens in place: files open on demand and only the bytes an application reads cross the link.
Both peers online. A share joins two machines that are both running.
Pairing across networks needs the relay. The free relay allows about 3 connection attempts per 5 minutes. On one local network no relay is involved.

Common questions

Do I need to pass a code every time?

No. KeibiDrop peers exchange an 86 character fingerprint once and connect on it afterwards. croc generates a fresh code phrase for each transfer.

Is there a GUI?

Yes, and a CLI with a JSON line per command for scripting and agents. croc is a command line tool with a browser page.

Can I see what is on the other machine?

Yes. KeibiDrop mounts the folder, so you browse it and pull only the files you open.

What happens if the relay is down?

A session that is already open keeps running, because the relay carries no file bytes. Peers on one local network still find each other by multicast. A new pairing across networks waits until the relay answers again.

Compared with Blip · Compared with LocalSend · Compared with Magic Wormhole · Network paths · Install