Croc: Securely Transfer Files Between Any Two Computers

TL;DR — Quick Summary

Croc is a CLI tool for securely sending files between any two computers. Uses PAKE encryption, works across NATs, and transfers at full network speed.

Croc is the simplest way to send files between computers. No accounts, no setup, no SSH. One command on each end, a code phrase in between, and your files transfer encrypted at full network speed.

Installation

# macOS
brew install croc

# Arch Linux
sudo pacman -S croc

# Go
go install github.com/schollz/croc/v10@latest

# Quick install (any platform)
curl https://getcroc.schollz.com | bash

# Windows (scoop)
scoop install croc

Basic Usage

Sender:

croc send document.pdf
# Output: Code is: castle-repair-pencil
# Share this code with the receiver

Receiver:

croc castle-repair-pencil
# File transfers with end-to-end encryption

That’s it. Two commands.

Advanced Usage

# Send multiple files
croc send file1.pdf file2.jpg folder/

# Use custom code
croc send --code mysecret document.pdf

# Send text instead of file
croc send --text "Hello from the other computer"

# Pipe stdin
cat database.sql | croc send

# Use specific relay
croc --relay my-relay.example.com:9009 send file.zip

# Self-host a relay
croc relay --ports 9009,9010,9011,9012,9013

How It Works

Sender generates a code phrase and connects to the relay
Relay holds the connection open (public relay at croc.schollz.com)
Receiver enters the code and connects to the relay
PAKE establishes end-to-end encryption using the code as the shared secret
Transfer happens encrypted — the relay cannot read the data
Files are compressed and sent at full network speed

Comparison

Feature	Croc	scp	rsync	Magic Wormhole	Firefox Send
Setup needed	None	SSH	SSH	None	Browser
Works across NAT	Yes	No	No	Yes	Yes
E2E encrypted	Yes	SSH	SSH	Yes	Yes
Resumable	Yes	No	Yes	No	No
Speed	Full line	Full line	Full line	Moderate	Upload dep.
Multiple files	Yes	Yes	Yes	Yes	Yes
Cross-platform	All	Unix	Unix	All	Browser
Self-hostable	Yes	Yes	Yes	Yes	Discontinued

Summary

Croc sends files between any two computers with a simple code phrase
End-to-end encrypted using PAKE — relay server cannot read data
Works across NATs/firewalls via relay servers (public or self-hosted)
No accounts, no SSH, no configuration required
Cross-platform: Linux, macOS, Windows, and more
Supports resumable transfers, multiple files, folders, and text

Guide & Instructions

Estimated Time: 5m

Tools Needed:

Croc
Terminal

Install Croc

Install with brew install croc, go install github.com/schollz/croc/v10@latest, pacman -S croc, or curl https://getcroc.schollz.com | bash.

Send a file

Run croc send filename.zip. Croc generates a code phrase like 'castle-repair-pencil'. Share this code with the receiver.

Receive a file

On the receiving computer, run croc castle-repair-pencil. The transfer begins with end-to-end encryption.

Send multiple files or folders

Use croc send file1 file2 folder/ to send multiple items. Croc automatically bundles and compresses them.

Use a custom code

Use croc send --code my-secret-code filename to set your own memorable code instead of a random one.

Frequently Asked Questions

What is Croc?

Croc is a command-line tool that allows any two computers to send files to each other securely. It uses PAKE (Password Authenticated Key Exchange) for end-to-end encryption, works across NATs/firewalls via relay servers, and requires no configuration or account.

How is Croc different from scp?

scp requires SSH access to the remote machine. Croc works between any two computers anywhere — no SSH, no accounts, no port forwarding. The sender generates a code phrase, the receiver enters it, and the transfer begins with end-to-end encryption.

Is Croc secure?

Yes, Croc uses PAKE (Password Authenticated Key Exchange) to establish end-to-end encryption. The relay server cannot read the data. The code phrase is used to derive the encryption key, so only someone with the code can decrypt the transfer.

Does Croc work behind NATs and firewalls?

Yes, Croc uses a relay server to facilitate connections between computers behind NATs/firewalls. You can use the default public relay or self-host your own for privacy.