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SSH public key parser

Inspect authorized_keys entries: algorithm, key length, fingerprints and restrictions.

Input
Output

SSH public key parser

Paste one or more lines from an authorized_keys file and this tool breaks each one down: the algorithm (RSA, Ed25519 or ECDSA), the key length in bits, the SHA256 and MD5 fingerprints, the trailing comment, and any restrictions such as command= or from= that precede the key type. It is built for auditing a server's authorized_keys file, reviewing a pull request that adds a deploy key, or double-checking a key before you hand it to a colleague.

Batch processing is built in: paste as many lines as you like and each is parsed independently, in the order they appear. Turn on "Report invalid lines" to see exactly which lines could not be parsed and why — an unrecognized key type, invalid Base64, or key data that does not decode into a complete key. "Detect duplicate keys" flags any line whose fingerprint repeats an earlier one, which is how the same key ends up granted access twice under different comments. "Warn on weak keys" flags RSA keys under 2048 bits and any DSA key, both of which modern SSH clients increasingly refuse outright.

Choose a plain table for reading at a glance, or JSON when you want to feed the result into another script or a CI check. Blank lines and lines starting with # are skipped, matching how OpenSSH itself reads the file, and Windows (CRLF) and Unix (LF) line endings are handled interchangeably.

Everything runs locally in your browser — nothing you paste here is uploaded anywhere, which matters for a tool that handles key material. Copy the result, download it as a .txt file, or send it straight to another tool's input to continue the audit.

FAQ

Which key types are supported?
ssh-rsa, ssh-ed25519, and ecdsa-sha2-nistp256/384/521. DSA (ssh-dss) keys are also recognized so they can be flagged as weak.
How is a weak key defined?
Any RSA key under 2048 bits, or any DSA key. Both fall short of what current SSH clients and servers consider acceptable.
Can it read a private key?
No. It only parses public keys in authorized_keys format — the single base64 line starting with ssh-rsa, ssh-ed25519 or ecdsa-sha2-*.
What do the command= and from= entries mean?
They are restrictions OpenSSH applies to that key alone — for example forcing one command to run, or limiting which source addresses may use it. The tool lists whatever restrictions precede the key type on the line.
Are my keys uploaded anywhere?
No. Parsing and fingerprinting happen entirely in your browser — the keys never leave your device.