What is X.509 Certificate Decoder?
Paste a certificate in PEM format and NewKit's X.509 decoder instantly shows you all its readable information: who it belongs to (subject), who issued it (issuer), its validity period with remaining days, the serial number, the signature and key algorithm, the subject alternative names (SAN) and the SHA-256 fingerprint.
It is the perfect tool to quickly verify whether an SSL/TLS certificate is valid or about to expire, check which domains it is valid for, or inspect the chain of trust before deploying. The certificate is parsed entirely in your browser with the Web Crypto API, so it is never sent to any server: it is safe even for production certificates.
Frequently asked questions
Is it free?
Yes, all NewKit tools are completely free.
Is my data sent to a server?
No. Processing happens 100% in your browser, so it is safe even for sensitive data.