CERTINITE · FREE SSL TOOLS

SSL Certificate Decoder

Read a PEM X.509 certificate locally: subject, issuer, expiry, SANs, fingerprints, key usage and basic constraints. Free certificate decoder without signup.

  • 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 one PEM certificate, including its BEGIN CERTIFICATE and END CERTIFICATE lines. The browser reads its X.509 fields and computes fingerprints locally. Decoding does not establish trust in the certificate.

What does this tool check?

  • Subject, issuer, serial number and UTC validity dates
  • SAN entries and SHA-256/SHA-1 fingerprints
  • Signature algorithm and public key details
  • Basic Constraints, Key Usage and Extended Key Usage

Common issues & how to fix them

Certificate and private key confusion

Use only the public certificate block. Never paste private keys into a decoder. This tool rejects private key blocks.

Wrong certificate role

Basic Constraints identifies CA certificates. Server certificates typically have serverAuth in Extended Key Usage. Check the CA’s issuance profile if these fields do not match your intended use.

Unexpected expiry date

Compare the decoded certificate with the certificate actually served by the website using the SSL Checker. You may have renewed a file without deploying it.

Frequently asked questions

Is decoding the same as verification?

No. The decoder reads fields and fingerprints. It does not check a trusted chain, revocation or hostname coverage against a live website.

Why show a SHA-1 fingerprint?

Some older administration tools use it as an identifier. A fingerprint is not the certificate’s signing algorithm. Prefer SHA-256 when comparing certificates.

Can I decode a bundle?

Decode one certificate at a time so the result is unambiguous. Use the chain checker to inspect a live server’s built validation path.

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