putty

SSH and Telnet terminal emulator

TLDR

Connect to SSH server

$ putty -ssh [user@host]

Connect with specific port

$ putty -ssh -P [2222] [user@host]

Load saved session

$ putty -load "[session_name]"

Connect via serial

$ putty -serial [/dev/ttyUSB0]

Use private key

$ putty -ssh -i [key.ppk] [user@host]

PuTTY is a free terminal emulator and network file transfer application supporting SSH, Telnet, SCP, and serial connections. Originally developed for Windows where no built-in SSH client existed, it has become one of the most widely used remote access tools and is also available on Linux and macOS.PuTTY stores connection profiles as saved sessions, allowing quick access to frequently used servers with preconfigured settings for port, protocol, key authentication, and terminal appearance. It uses its own PPK key format, though keys can be converted to and from OpenSSH format using the companion puttygen tool. The PuTTY suite includes plink for command-line connections, pscp and psftp for file transfer, and pageant for SSH agent key management.

PARAMETERS

HOST

Target hostname.

-ssh

Use the SSH protocol.

-telnet

Use the Telnet protocol.

-serial

Open a serial connection.

-raw

Use raw TCP (no protocol-level processing).

-rlogin

Use the Rlogin protocol.

-l USER

Specify login username.

-pw PASSWORD

Provide password on the command line (insecure; prefer -pwfile).

-pwfile FILE

Read password from the first line of FILE.

-P PORT

Port number.

-i KEY

Private key file (PPK format).

-load SESSION

Load a saved session by name.

-X / -x

Enable / disable X11 forwarding.

-A / -a

Enable / disable agent forwarding.

-C

Enable compression.

-L local:host:port

Forward a local port to a remote destination.

-R remote:host:port

Forward a remote port back to the local machine.

-D port

Open a SOCKS dynamic-port-forwarding listener.

-m FILE

Execute the contents of FILE on the remote host instead of an interactive shell.

-N

Do not start a shell or command (useful for port-forwarding only).

-nc host:port

Make a TCP connection through the SSH server instead of a shell.

-t / -T

Force / suppress pseudo-terminal allocation.

-agent / -noagent

Enable / disable Pageant authentication.

CONFIGURATION

~/.putty/sessions/

Saved session profiles containing connection settings, port, protocol, key file path, and terminal configuration.

~/.putty/sshhostkeys

Cache of SSH host keys for known servers, used to detect man-in-the-middle attacks.

~/.putty/sshkeys/

Directory for private key files in PPK format used for public key authentication.

CAVEATS

Uses the PPK key format; convert OpenSSH keys with puttygen. The -pw flag exposes the password to anyone who can read the process list — prefer -pwfile or key-based auth. PuTTY is also available on Linux and macOS.

HISTORY

PuTTY was created by Simon Tatham and first released in 1999. It became the standard SSH client on Windows, where no built-in SSH client was available until Windows 10 (2018).