Choosing the protocol

Short answer: you usually do not have to. The default, protocol: 'auto', asks the server for SFTP and falls back to SCP when it has none. client.protocol tells you which one it got.

protocol: 'auto' usesSFTP

client.fsavailable

Directory copiesfiles in parallel

The common case. Nothing to configure.

await connect({ host: 'example.com', username: 'deploy', privateKey });

How 'auto' decides

The SFTP probe costs one round trip right after login. SCP is only tried when you transfer, since it runs the scp program on the server for each operation.

What you get with each

	SFTP	SCP
upload(), download()	yes	yes
writeFile(), readFile()	yes	yes (streams without size are buffered)
client.fs (list, stat, mkdir, rm, rename)	yes	no, undefined
Parallel files in directory copies	yes, concurrency	no, one at a time
total in download progress	yes	no
Works on Dropbear, OpenWrt, network gear	only if an SFTP server is installed	yes
Works on SFTP only hosts (ForceCommand internal-sftp)	yes	no

Errors use the same codes on both, so ERR_NOT_FOUND means "not found" whichever protocol ran.

Force one

// Needs client.fs or many parallel files: fail early if SFTP is missing.
await connect({ ...options, protocol: 'sftp' });

// A device you know has no SFTP: skip the probe.
await connect({ ...options, protocol: 'scp' });

When scp is not on the remote PATH, point to it with scpCommand: '/usr/bin/scp'.

Want the background?

SCP or SFTP in 2026? explains how the two protocols work, what OpenSSH 9 changed and where each one still wins.