No supported authentication methods
What “No supported authentication methods” usually means
When PuTTY reports No supported authentication methods available, the client has already attempted a network or protocol step and failed before a normal interactive shell is available. This guide explains what the message usually means on Windows clients, which local settings to verify first, and when the problem is almost certainly on the server, firewall, or DNS path rather than inside the PuTTY GUI.
The server and client could not agree on any authentication method you can actually perform. Often the server offers publickey only while your client presents none, or methods are disabled by policy.
Independent resource: Putty.info is educational only and is not affiliated with the official PuTTY project. Compare symptoms against the official documentation for your installed version.
Symptoms you will see
Operators usually notice this failure in one of a few repeatable ways. Capture the exact dialog text, the hostname and port from the Session panel, and whether the failure happens before or after a username prompt—those details decide which checklist below applies.
- Failure naming unsupported or unavailable authentication methods.
- No password prompt when you expected one.
Likely causes ranked by frequency
Several independent conditions can produce the same client-facing wording. Work from the outside in: reachability first, protocol selection second, authentication third. Changing key files will not fix a TCP refusal, and opening a wider firewall will not fix a rejected public key.
- No key loaded and PasswordAuthentication no on server.
- Pageant not running; Auth panel empty.
- Server requires a key type your older PuTTY cannot offer.
- keyboard-interactive required but client settings interfere.
Step-by-step client checks
Use this ordered checklist on a workstation you control. Prefer saved sessions so Host Name, Port, and Connection type stay consistent while you isolate one variable at a time.
- Load the correct PPK in Connection → SSH → Auth or into Pageant.
- Confirm the public key is installed for the username you use.
- Upgrade PuTTY to a current stable release supporting modern key algorithms.
- Ask whether password auth is intentionally disabled.
- Enable auth logging on a test host to see offered vs attempted methods.
- Avoid random algorithm demotion; prefer upgrading clients and servers.
Do not paste private keys, passphrases, or production passwords into Putty.info tools or contact forms. Diagnose locally with PuTTY, Plink, PSCP, or PSFTP from an official install.
When it is a server or network issue
sshd_config PubkeyAuthentication, PasswordAuthentication, and AuthenticationMethods interact. Match blocks can require multiple factors. Publish onboarding docs that state which method is expected.
If TCP connects from another network path but fails from yours, involve the network team with traceroute/path evidence rather than repeatedly regenerating keys. If authentication fails after a banner appears, collect the server sshd logs for the same timestamp and username—client-side retries alone rarely reveal AccountLocked, Match blocks, or AllowUsers denials.