PuTTY

Overview

PuTTY is a free, open-source SSH and Telnet client, and one of the most classic and widely used remote login tools on the Windows platform. It is primarily used to securely connect to remote Linux/Unix servers, routers, network devices, etc., via the SSH protocol, and supports various protocols and functional extensions.

History and Development

• 1998: Simon Tatham (a Cambridge University graduate) began developing PuTTY as a personal project, initially as a simple SSH client.
• 1999: PuTTY 0.50 was released, the first public version, supporting SSH-1.
• 2000–2005: Rapid iteration, adding support for SSH-2, SFTP, port forwarding, key authentication, etc., becoming the de facto standard for SSH on Windows.
• 2007: PuTTY 0.60 was released, adding more encryption algorithms and security improvements.
• 2011: Version 0.62 began supporting IPv6.
• 2021: Version 0.76 was released, fixing over 20 security vulnerabilities and fully supporting modern encryption algorithms.
• October 15, 2024: PuTTY 0.81 was released (the current latest version), primarily fixing security issues, improving Windows 11 compatibility, and supporting new encryption algorithms (ChaCha20-Poly1305, etc.).
• Current Status: Simon Tatham remains the main maintainer, the project is very stable, and updates are released only 1-2 times a year (mainly for security fixes).

Main Features

1. Core Functionality
   • Full SSH-1 / SSH-2 support
   • Telnet, Rlogin, Raw, Serial (COM port) connections
   • SFTP / SCP file transfer (built-in psftp.exe / pscp.exe)
   • Port forwarding (local/remote/dynamic)
   • Public key authentication (supports PuTTY .ppk and OpenSSH .pub/.pem formats)
2. Interface and Usability
   • Classic windowed interface (session configurations can be saved for one-click connection)
   • Supports custom colors, fonts, and window sizes
   • Supports UTF-8 and Chinese character display (requires correct setting of character encoding to UTF-8)
3. Security Features
   • Supports modern encryption: AES, ChaCha20, Curve25519, Ed25519, etc.
   • Supports key agent (Pageant)
   • Supports certificate authentication (new in PuTTY 0.81)
4. Portability
   • Fully portable version (no installation required, simply extract and run)
   • Can be carried on a USB drive
5. Derivative Tools
   • PuTTYgen: Generate/convert key pairs
   • Pageant: SSH key agent (enter password once, effective globally)
   • psftp: Command-line SFTP client
   • pscp: Command-line SCP transfer tool

Advantages and Limitations

Advantages

• Extremely small size and fast startup: 3–5 MB, opens almost instantly
• Completely free and open source: MIT license, no restrictions
• Extremely stable: 30 years of history, almost no crashes
• Comprehensive functionality: Almost everything an SSH client should have
• Strong portability: No installation required, suitable for IT professionals to carry with them
• Native Windows experience: More user-friendly than PuTTY's Linux alternatives (such as the ssh command)

Limitations

• Outdated interface: Classic Windows 95 style (many people complain it's ugly, but functionality-focused users don't care)
• No built-in multi-tab terminal: Requires manually opening multiple windows (third-party wrappers like MTPuTTY can be used)
• Does not remember passwords by default: Requires using Pageant or external tools for password management
• Compared to modern tools:
  • MobaXterm: Beautiful interface, multi-tab support, SFTP Browsers
  • Windows Terminal + OpenSSH: Microsoft's native solution, modern but complex to configure
  • Tabby/PowerShell: More modern alternatives
  • VS Code Remote-SSH: The preferred choice for developers

Summary

PuTTY is the oldest, most classic, and most reliable SSH client on the Windows platform. The latest version 0.81 (released in 2026) remains a standard tool for countless operations engineers, developers, and server administrators. It is small, fast to start, stable, and completely free and open-source, suitable for any scenario requiring SSH login to Linux/Windows servers.