What is PuTTY?

PuTTY is a client program for the SSH, Telnet, Rlogin, and SUPDUP network protocols.

These protocols are all used to run a remote session on a computer, over a network. PuTTY implements the client end of that session: the end at which the session is displayed, rather than the end at which it runs.

In really simple terms: you run PuTTY on a Windows machine, and tell it to connect to (for example) a Unix machine. PuTTY opens a window. Then, anything you type into that window is sent straight to the Unix machine, and everything the Unix machine sends back is displayed in the window. So you can work on the Unix machine as if you were sitting at its console, while actually sitting somewhere else.

Features supported in PuTTY

In general, if you want to know if PuTTY supports a particular feature, you should look for it on the PuTTY web site. In particular:

• try the changes page, and see if you can find the feature on there. If a feature is listed there, it's been implemented. If it's listed as a change made since the latest version, it should be available in the development snapshots, in which case testing will be very welcome.

• try the Wishlist page, and see if you can find the feature there. If it's on there, and not in the ‘Recently fixed’ section, it probably hasn't been implemented.

Does PuTTY support SSH-2?

Yes. SSH-2 support has been available in PuTTY since version 0.50 in 2000.

Public key authentication (both RSA and DSA) in SSH-2 was new in version 0.52 in 2002.

A.2.2 Does PuTTY support reading OpenSSH or ssh.com SSH-2 private key files?

PuTTY doesn't support this natively (see the wishlist entry for reasons why not), but as of 0.53 PuTTYgen can convert both OpenSSH and ssh.com private key files into PuTTY's format.

Does PuTTY support SSH-1?

Yes. SSH-1 support has always been available in PuTTY.

However, the SSH-1 protocol has many weaknesses and is no longer considered secure; you should use SSH-2 instead if at all possible.

As of 0.68, PuTTY will no longer fall back to SSH-1 if the server doesn't appear to support SSH-2; you must explicitly ask for SSH-1.

Does PuTTY support local echo?

Yes. Version 0.52 has proper support for local echo.

In version 0.51 and before, local echo could not be separated from local line editing (where you type a line of text locally, and it is not sent to the server until you press Return, so you have the chance to edit it and correct mistakes before the server sees it). New in version 0.52, local echo and local line editing are separate options, and by default PuTTY will try to determine automatically whether to enable them or not, based on which protocol you have selected and also based on hints from the server. If you have a problem with PuTTY's default choice, you can force each option to be enabled or disabled as you choose. The controls are in the Terminal panel, in the section marked ‘Line discipline options’.

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