CERTINITE · FREE SSL TOOLS

CSR Decoder & Signature Validator

Decode a PEM certificate signing request in your browser. Inspect subject fields, SANs, key details and verify the CSR signature without uploading it.

  • No signup required
  • Full results, always free
  • Built for IT & DevOps

Use this tool free, without an account

Enable JavaScript to use the interactive tool. Instructions and troubleshooting guidance are available below.

How it works

Paste a PEM block starting with BEGIN CERTIFICATE REQUEST. The isolated browser tool parses PKCS#10 and verifies the signature with the public key embedded in the request. No CSR is sent to Certinite.

What does this tool check?

  • Common Name, Organization, Organizational Unit, Country, State and Locality
  • Requested Subject Alternative Names
  • Public key algorithm and size
  • CSR signature algorithm and cryptographic signature validity

Common issues & how to fix them

Malformed CSR

Copy the complete PEM block including its BEGIN and END lines. A certificate or private key is not a CSR. Avoid copying editor formatting or truncating base64 lines.

Invalid signature

Regenerate the CSR using the original private key on your own machine. Changing the subject or SANs after signing invalidates the signature.

Incorrect domain information

Correct the subject and SAN configuration before generating a new request. Your CA decides which requested attributes it will include in the issued certificate.

Frequently asked questions

Do I need to paste my private key?

No. A CSR contains the public key needed to verify its own signature. Private key input is rejected.

Does a valid signature prove domain ownership?

No. It proves the request was signed by the corresponding key. The CA must still perform its own domain or organization validation.

Where is my CSR processed?

Inside a sandboxed browser frame with network access disabled. The parent page receives only a success/failure event and frame size, never the input or decoded fields.

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