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SSL Certificate Key Matcher

Paste a certificate and a private key, plus a CSR if you like, to see whether they form one key pair.

Your text and files never leave your browser — nothing is sent to a server.

Fill in at least two boxes to compare them.

    How to use

    1. Paste the certificate into the first box and the private key into the second, or drop the files onto them. Add a CSR only if you want to compare it too.
    2. The public key is extracted from each item and compared. A match shows in green, a mismatch in red.
    3. If you paste a password-protected key (ENCRYPTED PRIVATE KEY, legacy OpenSSL or OpenSSH), a password field appears and the key is unlocked inside your browser.
    4. Checking before you install a certificate saves you from the “key values mismatch” error that stops a web server from starting.

    FAQ

    Is it safe to paste a private key here?

    Everything runs inside this browser tab and nothing, including your key, is sent to a server or stored. It disappears when you close the page. Still, avoid doing this on a shared computer.

    How is the match checked?

    The public key inside the certificate and CSR is compared with the public key derived from the private key: the modulus and exponent for RSA, the curve and public point for ECDSA. It is the same idea as comparing openssl modulus output.

    What should I do if they do not match?

    The certificate was probably issued for a different CSR, or the key comes from another server. Find the private key that was created together with the CSR you submitted, or generate a new key and CSR and have the certificate reissued.

    Which key formats are supported?

    PKCS#8 (BEGIN PRIVATE KEY), PKCS#1 for RSA (BEGIN RSA PRIVATE KEY), SEC1 for EC (BEGIN EC PRIVATE KEY) and OpenSSH keys (BEGIN OPENSSH PRIVATE KEY). Password-protected PKCS#8, legacy OpenSSL-encrypted keys (Proc-Type) and passphrase-protected OpenSSH keys are unlocked once you enter the password.

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