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Certificate Viewer

Inspect standard X.509 certificates (.pem, .crt, .cer) securely in your browser.

Input Certificate

— OR PASTE PEM TEXT —

Certificate Details

Details will appear here once a certificate is parsed.

About the X.509 Certificate Viewer

What is the X.509 Certificate Viewer?

The X.509 Certificate Viewer is a free, client-side utility designed for developers, system administrators, and security professionals. It allows you to securely parse, decode, and inspect SSL/TLS certificates directly in your web browser. Because digital certificates are a critical component of your security infrastructure, this tool ensures absolute privacy: the parsing engine runs entirely on your local machine using JavaScript. Whether you drag and drop a file or paste raw text, your certificate data is never uploaded to an external server.

Why Inspect SSL/TLS Certificates?

Troubleshooting secure connections (HTTPS) often requires looking "under the hood" of your certificate files. Instead of relying on complex OpenSSL command-line prompts, this visual inspector allows you to instantly verify crucial security details:

  • Check Expiration Dates: Instantly see the "Valid From" and "Valid To" timestamps to ensure your certificate hasn't expired, avoiding browser security warnings for your users.
  • Verify Domain Coverage: SSL certificates often cover multiple domains or subdomains. The viewer extracts the Subject Alternative Names (SANs) so you can confirm every URL is protected.
  • Confirm the Issuer: Ensure the certificate was generated by the correct Certificate Authority (CA) and wasn't accidentally self-signed or compromised.
  • Audit Key Strength: View the public key algorithm (e.g., RSA) and its bit length (e.g., 2048 or 4096 bits) to ensure it meets modern cryptographic standards.

Supported Formats

This tool supports the standard PEM (Privacy-Enhanced Mail) format, which is the most common format for X.509 certificates. These are Base64-encoded ASCII files that typically carry extensions like .pem, .crt, or .cer, and are enclosed by -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- tags. If you upload a binary DER-encoded certificate, the tool's smart-detection will attempt to automatically convert it into a readable PEM format before parsing the structural ASN.1 data.

What Information is Decoded?

Once parsed, the tool breaks down the certificate payload into human-readable properties:

  • Subject & Issuer: Displays the Common Name (CN), Organization (O), and Country (C) of both the entity the certificate belongs to and the authority that signed it.
  • Validity Status: Automatically compares the certificate's validity window against your system's current clock to display a live Valid, Expired, or Not Yet Valid status.
  • Serial Number: The unique identifier assigned by the CA.
  • SHA-1 Fingerprint: The cryptographic hash of the entire certificate, commonly used to verify that the file hasn't been tampered with or corrupted during transit.