TLS / SSL Certificate Decoder
Paste a PEM, see subject, issuer, validity, SANs, key info and extensions.
Paste a PEM-encoded certificate (the -----BEGIN CERTIFICATE----- block). We parse the ASN.1 and surface the fields that actually matter when something is wrong.
Runs entirely in your browser — nothing you enter is sent to a server.
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Subject & issuer (RFC 4514 DN), validity dates, public-key algorithm and size, signature algorithm, Subject Alternative Names, basic constraints, key usage, extended key usage, and the issuer's key identifier.
Built by WeWorkWorldwide — a senior software team in Romania & Pakistan that ships deep technical work. Need this turned into something production-grade for your stack? Talk to our engineers →