What are some edge cases for Certificate Decoder?

Expired or not-yet-valid certificates. Wildcard DNS and multi-SAN SSL certificates.

Is this Certificate Decoder safe for sensitive data & credentials?

Yes, 100%. All processing runs client-side in your local browser memory. No text, tokens, payloads, or logs are ever transmitted to any remote server or analytics engine.

Can I use Certificate Decoder offline without internet?

Yes. Because this tool runs strictly on client-side JavaScript with zero external API calls, once the web application is loaded in your browser it will continue working offline.

How does URL state sharing work?

When you click Share Payload, your state is encoded directly into a URL hash fragment (#data=...) without storing anything on a database server.

X.509 Certificate & CSR Decoder Online — 100% Private SSL Inspector

Decode and inspect X.509 SSL/TLS certificates and CSR requests in your browser. View Subject Alternative Names (SANs), expiry dates, fingerprints, and key usages.

How to use

Paste a PEM certificate (-----BEGIN CERTIFICATE-----) or CSR (-----BEGIN CERTIFICATE REQUEST-----), or upload a .crt/.pem file.
Instantly inspect certificate status, validity countdown, Common Name, and Issuer.
Review Subject Alternative Names (SANs) and Cryptographic Properties (Key size, algorithm, SHA-256 fingerprint).

Important Considerations

Expired or not-yet-valid certificates.
Wildcard DNS and multi-SAN SSL certificates.

Privacy Notice: This tool is strictly client-side. All processing runs in your local browser memory using JavaScript. No text, tokens, payloads, or logs are ever transmitted to any remote server or analytics engine. You can even use this tool completely offline.

X.509 Certificate & CSR Decoder (Offline & Secure)

How to use

Important Considerations

Keyboard Shortcuts

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