MyWebUtils: Free Online Dev Tools

SSL Certificate Decoder
Paste or upload a PEM-encoded SSL certificate to view its details.
Paste or upload a PEM certificate to see its details.
About the SSL Certificate Decoder

What is an SSL/TLS Certificate?

An SSL/TLS certificate is a digital file that authenticates a website's identity and enables an encrypted connection. It's the "S" in HTTPS that signifies a secure connection. These certificates are issued by trusted Certificate Authorities (CAs) and contain crucial information about the website's owner and the certificate's validity.

Certificates are often shared in PEM (Privacy-Enhanced Mail) format, which is a Base64-encoded text file starting with `-----BEGIN CERTIFICATE-----`.

Why Do Developers Need to Decode a Certificate?

  • Troubleshooting SSL Errors: If a user reports a security warning, a developer can paste the certificate to quickly check if it's expired, issued to the wrong domain, or has an incomplete chain.
  • Verifying Certificate Details: Before installing a certificate on a server, it's good practice to decode it and verify that the Subject (domain name), Issuer, and validity dates are all correct.
  • Inspecting SANs: Check the Subject Alternative Names (SANs) to see all the domains and subdomains the certificate is valid for.
  • Security Audits: Quickly check the signature algorithm and public key size to ensure they meet current security standards.

How This Tool Helps

This tool allows you to paste the PEM-formatted text of a certificate (or upload the `.crt`/`.pem` file) and see its contents in a human-readable format.

Developer Note: Full, secure parsing of X.509 certificates is a complex cryptographic operation. This tool currently demonstrates the UI for such a decoder using placeholder data. For a real-world implementation, libraries like `@peculiar/x509` or `pkijs` would be used in the browser to safely parse the certificate data without sending it to a server.