What certificate formats are supported?

PEM-encoded certificates (the format with -----BEGIN CERTIFICATE----- headers) are fully supported. DER certificates can be converted to PEM first using the DER to PEM converter.

Can I decode a certificate chain?

Yes. Paste multiple PEM certificates and each one in the chain is decoded separately.

Is my certificate data private?

Yes. Parsing runs entirely in your browser. No certificate data is sent to any server.

Best Free SSL Certificate Decoder

SSL/TLS certificates contain critical information — issuer, subject, SANs, validity dates, key algorithm, and extensions — that is encoded in ASN.1 and not human-readable without a decoder. devtoolkit.sh's SSL Certificate Decoder parses any PEM-encoded certificate and displays all fields in a clean, readable layout: subject and issuer distinguished names, Subject Alternative Names, validity period, public key type and size, signature algorithm, key usage extensions, and fingerprints. Paste a certificate from a server, from a downloaded file, or from a keystore export and get full details instantly. All decoding runs in your browser — certificates are never sent to any server.

PEM Certificate

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FAQ

What certificate formats are supported?: PEM-encoded certificates (the format with -----BEGIN CERTIFICATE----- headers) are fully supported. DER certificates can be converted to PEM first using the DER to PEM converter.
Can I decode a certificate chain?: Yes. Paste multiple PEM certificates and each one in the chain is decoded separately.
Is my certificate data private?: Yes. Parsing runs entirely in your browser. No certificate data is sent to any server.