SSL Certificate Decoder

SSL certificates are the foundation of secure HTTPS connections, containing cryptographic keys, domain information, and validity dates. The SSL Certificate Decoder is a browser-based tool that extracts and displays all essential details from X.509 certificates in PEM format, allowing developers, sysadmins, and security professionals to inspect certificate contents without specialized software or command-line tools.

To use the tool, paste your certificate's PEM text (the block starting with "-----BEGIN CERTIFICATE-----") into the input area and click Decode. The tool parses the certificate structure and presents information such as issuer name, subject domain, expiration date, public key details, and signature algorithm in a readable, organized format. This is especially useful for troubleshooting HTTPS errors, verifying certificate validity before deployment, and auditing security configurations.

The decoder works entirely in your browser—no data is sent to any server—making it safe for sensitive certificates. While this tool excels at decoding standard X.509 certificates, it cannot verify chain trust or validate certificate signatures; for those tasks, you would use your web server's native tools or a full PKI validation service.