Developer / Certificates
Certificate Key Matcher
Compare a certificate with an RSA or EC private key and/or CSR to find whether their public keys match, entirely in your browser.
Certificate Key Matcher: Extracts each public key, puts it into a consistent representation and compares it with the certificate’s public key. RSA and EC are supported, including PKCS#8 private keys, RSA PKCS#1 private keys and EC keys with named-curve parameters. Runs 100% locally in your browser with zero server file uploads.
- Category
- Developer tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Keys and certificates stay in your browser. Matching keys does not establish certificate trust or expiry.
Public key representation
RFC 5280 (https://www.rfc-editor.org/rfc/rfc5280) describes the public key information carried by certificates. Comparing its normalised representation identifies the same key across a certificate and request.
Private key formats
RFC 5208 (https://www.rfc-editor.org/rfc/rfc5208) describes PKCS#8, while RFC 5915 (https://www.rfc-editor.org/rfc/rfc5915) describes EC private keys. This page accepts unencrypted keys and does not ask for a passphrase.
How to use it
- Paste one PEM certificate.
- Paste an unencrypted private key, a CSR, or both.
- Compare public keys and read the result for each supplied object.
Privacy & limitations
Everything runs in your browser. Your images, keys and pasted data are not uploaded or saved by this tool.
Related tools
Frequently asked questions
Does matching mean the certificate is trusted?
No. Matching only compares public keys. It does not verify the certificate signature, expiry, hostname or chain of trust.
Are encrypted private keys supported?
No. Use an unencrypted PEM key. Keys are processed only in your browser and are not uploaded or saved.
Can I compare a CSR without the private key?
Yes. Paste the certificate and CSR to compare their public keys. If you also supply a private key, its result is reported separately.
Free tool · runs in your browser · no account required