Certificate Decoder
Read an X.509 certificate, chain or CSR, and see who it is for and when it expires.
How to decode a certificate
- Paste the PEM text, or drop a certificate file.
- Read each certificate in the chain, from your site's certificate up to the root.
- Check the expiry and fingerprints, and copy what you need.
Questions
Which files can it read?
PEM text with one or more certificates, single certificates as .pem, .crt, .cer or .der, and certificate requests as .csr.
Is my certificate uploaded?
No. It is read inside your browser and never leaves your device.
When does it warn about expiry?
When a certificate expires within 30 days, and when it has already expired or is not valid yet.
Does it check that the chain is trusted?
No. It shows what each certificate says; it does not ask any server whether to trust it.