Certificate Decoder
See who an SSL certificate is for, and when it expires.
Questions
What can I paste?
PEM text (the blocks starting with -----BEGIN CERTIFICATE----- or -----BEGIN CERTIFICATE REQUEST-----), several at once for a chain, or plain base64. You can also open .pem, .crt, .cer and .der certificates, .csr requests and .p7b bundles.
Is it safe to paste a certificate here?
Yes: certificates and CSRs are public by design, and this page doesn’t send them anywhere. Never paste a private key into any website; if you do by mistake, this tool warns you and ignores it.
What does “chain order” mean?
A server should send its own certificate first, then each certificate that signed the previous one. When you paste a chain, each step is checked: the issuer of one certificate must be the subject of the next.
Does it check whether a certificate is trusted or revoked?
No. That needs your browser’s list of trusted roots and online revocation checks, which would reveal what you’re checking. The tool shows the facts and flags what’s wrong from the certificate alone: expiry, weak algorithms, short keys.
Is it free? Do I need an account?
It is free to use and there is nothing to sign up for. There are no watermarks and no daily limits.
Missing something, or not working as it should? Tell us