100% Client-Side

SSL Certificate Decoder

Free online SSL certificate decoder. Parse and inspect PEM X.509 certificates to view subject, issuer, validity, and serial number. — runs 100% in your browser, client-side only. No data is sent to any server. Free to use, no account required.

Free Client-Side No Login No Storage
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How to Use the SSL Certificate Decoder

  1. Paste a PEM-encoded certificate (starts with -----BEGIN CERTIFICATE-----).
  2. Click Decode Certificate to extract details.
  3. View subject, issuer, validity dates, serial number, and more.

Uses a lightweight client-side ASN.1 DER parser. No data sent to any server.

What is SSL Certificate Decoder?

PEM (Privacy Enhanced Mail) is a Base64-encoded format used for SSL certificates, private keys, and public keys. A PEM decoder parses these files to reveal the underlying certificate details — validity dates, issuer, subject, and key type.

Common Uses

  • Inspecting SSL certificate expiry dates
  • Verifying certificate chains
  • Debugging TLS handshake issues
  • Confirming a certificate matches its private key

Frequently Asked Questions

What is a PEM Decoder?

PEM (Privacy Enhanced Mail) is a Base64-encoded format used for SSL certificates, private keys, and public keys. A PEM decoder parses these files to reveal the underlying certificate details — validity dates, issuer, subject, and key type.

Why use CipherKit's PEM Decoder?

Your private keys and certificates never leave your browser. This is critical — pasting PEM files into unknown online tools exposes your private key infrastructure. CipherKit processes everything locally.

When to use this tool

Use when inspecting SSL certificate expiry, verifying certificate chains, debugging TLS handshake issues, or confirming a certificate matches its private key.