SSL Certificate Decoder
Quickly decode SSL certificates (PEM/CER/CRT) to inspect security details, expiration dates, and domain ownership. All parsing happens locally in your browser.
100% Private & Secure
This tool runs completely inside your browser using client-side WebAssembly and JS. Zero data is ever sent to our servers.
How to use this tool
- Retrieve your certificate file (often ending in .pem, .crt, or .cer).
- Open it in a text editor and copy the text between -----BEGIN CERTIFICATE----- and -----END CERTIFICATE-----.
- Paste the code into the decoder above.
- Review the Expiration Date and Subject Alternative Names to ensure validity.
Example Usage
-----BEGIN CERTIFICATE----- MIIDRjCCAi6gAwIBAgIUS8E6I2K4M2I4M2I4M2I4M2I4M2I4MA0GCSqGSIb3DQEB ...
Subject: CN=devtoolslabs.com Issuer: CN=devtoolslabs.com Valid To: March 15, 2027
When to use this tool
- Verify SSL certificate expiration dates before production deployment.
- Inspect Subject Alternative Names (SANs) to confirm domain coverage.
- Debug 'Insecure' browser warnings by checking issuer chains.
- Audit development and staging certificates for security compliance.
Frequently Asked Questions
Is it safe to paste my certificate here?
Yes. This tool uses the `node-forge` library to parse the raw data directly in your browser. No data is sent to our servers, keeping your security information private and secure.
What is a PEM file?
PEM (Privacy Enhanced Mail) is the most common format for certificates. It is a Base64 encoded string wrapped in headers like `BEGIN CERTIFICATE`.
What are Subject Alternative Names (SANs)?
The SAN extension allows a single SSL certificate to protect multiple domains, such as `example.com` and `api.example.com`. Our decoder lists all of these for easy verification.
Can I decode a .crt or .cer file?
Yes, as long as the file is text-based (PEM format). If your .crt file starts with '-----BEGIN CERTIFICATE-----', you can paste it directly.
How do I check if my SSL certificate is expired?
Paste your certificate into the decoder. The 'Valid To' section will show the expiration date. Our tool will highlight the date in red if the certificate has already expired.
What does the SHA-256 Fingerprint represent?
The fingerprint is a unique hash of the entire certificate. It is used by developers to uniquely identify a certificate for certificate pinning or audit logging.
Why does my certificate say 'RSA (2048 bits)'?
This describes the public key algorithm and its strength. RSA is the standard for web encryption, and 2048 bits is currently the minimum recommended length for modern security.
Does this tool work for Wildcard certificates?
Yes. Wildcard certificates (e.g., *.example.com) will be correctly identified in the Subject and Subject Alternative Names (SAN) fields.
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