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SSH Key Fingerprint

SHA256 and MD5 Fingerprints From an authorized_keys Line, Exactly as ssh-keygen Prints Them

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How the SSH Key Fingerprint works

This SSH key fingerprint tool reads OpenSSH public keys, one per line, and prints the SHA256 and MD5 fingerprints that ssh-keygen -lf would show. Paste a whole authorized_keys file to identify every key in it, match a key against a server prompt or find the entry you need to remove.

How an SSH key fingerprint is calculated

An OpenSSH public key line holds a type, a base64 blob and an optional comment. The fingerprint is a hash of the decoded blob, not of the text line, so the comment and spacing never change it. Modern OpenSSH shows SHA256 in unpadded base64 with a SHA256: prefix. Older versions and some control panels still show MD5 as sixteen colon-separated hex pairs, so both are listed.

The tool supports RSA, Ed25519, ECDSA on P-256, P-384 and P-521, and the security-key types sk-ssh-ed25519 and sk-ecdsa-sha2-nistp256. Options in front of a key, such as from= or command= in authorized_keys, are skipped. Everything runs in your browser and public keys are not secret, but nothing is uploaded either way.

FAQ

Why does GitHub show a different fingerprint format?

GitHub and current OpenSSH show SHA256 fingerprints, while older tools such as PuTTY or some hosting panels show MD5 hex. They are two hashes of the same key blob, so compare like with like. This tool prints both so you can match whichever format you were given.

Can I fingerprint a private key here?

Paste only the public half. If you have just the private key, run ssh-keygen -y -f id_ed25519 locally to print its public key, then paste that. Private keys should never be pasted into web pages, even ones that run locally like this one.

How do I check a host key fingerprint?

Run ssh-keyscan host to fetch the server's public keys, paste the output here and compare the SHA256 value with the one the provider publishes or the one ssh shows on first connect. A mismatch means you may be talking to a different machine.

See also: all Security & Identifiers tools, Dev Utilities, Formatters & Validators, Data & Encoding, SEO, Accessibility, AI.

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