SSL Certificate Decoder
Decode a PEM / X.509 certificate.
Runs entirely in your browser — nothing you enter is uploaded, logged, or tracked.
Paste a PEM certificate (-----BEGIN CERTIFICATE-----) to decode it on your device — subject and issuer, the validity window, serial number, signature and public-key algorithms, the Subject Alternative Names, and the SHA-256 fingerprint. Unlike online cert decoders, your certificate is parsed locally and never sent to a server.
Frequently asked questions
Is my certificate uploaded?
No — it is parsed entirely in your browser. Even though a certificate is public, many online decoders send it to their server; this one does not.
What does it show?
Subject and issuer (CN, O, etc.), not-before/not-after dates, serial number, signature algorithm, public-key type and size, Subject Alternative Names, and the SHA-256 fingerprint.
Can it decode a private key or CSR?
It decodes X.509 certificates (the public cert). Private keys are not decoded — and you should not paste them into any web tool.