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TabBench

SSL Certificate Decoder

Decode X.509 SSL/TLS certificates and CSRs in your browser without uploading private credentials.

Runs in your browser. Nothing you add is uploaded.

What the SSL Certificate Decoder does

Transport Layer Security (TLS) certificates secure web applications, APIs, and enterprise communication. Inspecting certificate parameters before deploying or debugging handshake failures is critical. This client-side decoder parses PEM-encoded X.509 certificates and CSRs, calculating expiration countdowns, subject alternative names (SANs), serial numbers, and cryptographic fingerprints without uploading your credentials to any third-party server.

How to decode an SSL certificate or CSR

  1. Paste the raw PEM certificate starting with '-----BEGIN CERTIFICATE-----' or choose a sample certificate.
  2. Review the Days Remaining status badge to verify whether the certificate is active or expired.
  3. Inspect the Subject (Issued To) and Issuer (Certificate Authority) distinguished names.
  4. Check all secured domains under the Subject Alternative Names (SAN) list.
  5. Verify public key algorithms, key lengths, signature algorithms, and copy the SHA-256 fingerprint.

The SSL Certificate Decoder runs entirely in your browser — nothing you enter is uploaded, stored, or logged.

When to use it

Certificate Expiration & Renewal Audits

Prevent catastrophic production outages by checking exact expiration timestamps and remaining days before certificates expire.

Verifying Multi-Domain SAN Coverage

Confirm that wildcard certificates (*.domain.com) and additional subdomains are correctly included in the certificate extension before binding to a reverse proxy.

CSR Validation Before CA Signing

Inspect Certificate Signing Requests (CSRs) to verify that country codes, common names, and key algorithms match requirements prior to purchasing an expensive certificate.

Good to know

  • Never paste your private key anywhere. This tool only requires the public certificate or CSR.
  • Most modern CAs issue 90-day to 398-day certificates to maintain strict cryptographic freshness.
  • The SHA-256 fingerprint can be compared directly against browser security indicators to verify certificate pinning.

Frequently asked questions

Is it safe to paste certificates into this tool?

Yes. TabBench decodes X.509 certificates entirely client-side using JavaScript in your browser tab. No certificate data or domain names are ever transmitted to any server.

What does SAN mean in an SSL certificate?

Subject Alternative Name (SAN) is an X.509 extension that allows a single SSL certificate to secure multiple domain names, subdomains (like *.example.com), and IP addresses.

Can an SSL certificate be decoded without the private key?

Yes. Certificates are public documents distributed freely to any client that connects. They contain public keys and identity metadata; the private key remains confidential on the origin server.

What is an intermediate certificate?

Intermediate certificates link the leaf certificate on your server to a trusted Root CA pre-installed in operating system and browser trust stores, establishing an unbroken chain of trust.

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