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Certificate decoder

Paste PEM, DER, CSR or PKCS#7: subject, SANs, key, signature, extensions, validity and fingerprints, decoded in your browser.

Runs in your browser; nothing is uploaded

Maximum 512 KiB. Files and pasted keys stay in browser memory. Private key matching accepts unencrypted PKCS#8 only.

Read certificates locally

Inspect X.509 certificates, certificate signing requests and certificates inside PKCS#7 SignedData. The decoder shows names, SANs, public key and signature algorithms, validity, extensions and certificate fingerprints. Paste multiple certificates to check whether each issuer matches the next subject. This is an order check, not a trust or signature validation.

Check a private key

Paste an unencrypted PKCS#8 private key with a certificate or CSR to test whether the public and private keys match. The key is used only for an in-memory sign and verify check. Avoid exporting or sharing the pasted key.

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