Certificate Key Matcher

Verify that your SSL certificate matches its private key or CSR by comparing modulus hashes — an essential step before installing SSL on your server.

100% Free Modulus Hash Matching Cert + Key + CSR

Select what you want to match

Modulus MatchingCryptographically accurate check

3-Way MatchCert, key, or CSR combos

Nothing StoredKeys never logged

Instant ResultMatch check in milliseconds

Secure by designYour certificate and key data are processed instantly over an encrypted connection and never stored on our servers.

Encrypted in transitSubmitted over HTTPS/TLS — nothing is sent in plain text.

Never storedNeither the certificate nor the private key is saved to any database or log.

No third-party sharingYour data is never shared with ads, trackers, or outside services.

Processed instantlyChecked on request and discarded immediately after the response.

About Certificate Key Matcher

What Is a Certificate Key Matcher?

A certificate key matcher confirms whether an SSL certificate and a private key actually belong together — a mismatch between the two is a common cause of SSL installation failures, and this check catches it before you deploy.

How to Use the Certificate Key Matcher

Paste your certificate
Paste your private key
Click Check Match
Review whether they match

Key Features

Instant match verification — avoid a failed SSL install from a mismatched pair
Works without command-line OpenSSL

Who Uses This Tool

System administrators verify a certificate/key pair before installing it on a production server. Developers troubleshoot SSL handshake failures caused by mismatched files.

Frequently Asked Questions

Why would my certificate and key not match?
This typically happens when a new certificate was issued for a different CSR/key pair, or files from different requests got mixed up during setup.

Is this tool free?
Yes, checking certificate/key match is completely free.

Frequently Asked Questions

Why does certificate/key matching matter?

When installing SSL on a server, you must provide the certificate and its corresponding private key. If they don't match, the server will refuse to start or throw an SSL handshake error. This tool lets you verify they match before attempting installation.

How does modulus matching work?

RSA certificates, private keys, and CSRs each contain a modulus — the product of two prime numbers used in RSA cryptography. If the modulus of a certificate equals the modulus of its private key, they are a matching pair. We compare MD5 hashes of the modulus for a quick check.

Is it safe to paste my private key here?

The key is sent over HTTPS and never stored or logged. That said, for maximum security, you can use OpenSSL locally: openssl rsa -noout -modulus -in key.pem | md5sum and compare with openssl x509 -noout -modulus -in cert.pem | md5sum.

What if the certificate and key don't match?

You have the wrong key for your certificate. Common causes: you generated a new CSR+key after already submitting the original CSR to the CA, or you have multiple key files. Check which key file was used when you originally generated the CSR, or reissue the certificate with a new CSR+key pair.