SSL Certificate Decoder — Paste PEM

Paste a certificate and read the subject, issuer, validity window, subject alternative names and key details in plain text.

How to use
  1. Paste the certificate PEM block.
  2. The fields are decoded and listed.
  3. Read the subject, issuer, dates and SAN list.
Frequently asked questions
What is the SAN list and why does it matter?
Subject alternative names, the domains the certificate is actually valid for. Browsers ignore the common name entirely now, so a missing SAN entry is a hard failure.
What is the difference between subject and issuer?
Subject is who the certificate is for, issuer is the authority that signed it. A certificate where the two match is self-signed.
Does this verify the chain?
No. It decodes what is in the block you pasted. Whether the issuer is trusted and the chain is complete is a separate check against the intermediates.
How do I get the certificate from a live site?
Run openssl s_client -connect host:443 and copy the block between BEGIN and END, or export it from the browser's certificate viewer.
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