PEM Certificate Viewer
Paste an X.509 PEM certificate to extract and display its information: subject, issuer, validity, signature algorithm and public key.
PEM Certificate Viewer: Analyze Your X.509 Certificates Online
Why Use a PEM Certificate Viewer?
Quickly verifying certificate information (subject, issuer, validity dates) without resorting to the OpenSSL command line saves valuable time during deployment or troubleshooting.
This tool runs entirely in your browser: no certificate data is sent to any server, ensuring complete privacy of your keys and certificates.
Visual decoding of ASN.1 fields (serial number, signature algorithm, public key size) makes security audits and certificate compliance checks much easier.
Common Use Cases
- SSL/TLS Certificate Verification
- Paste your web server certificate to confirm that the Common Name (CN), validity dates, and signature algorithm match your expected configuration.
- Certificate Chain Debugging
- Analyze each certificate in the chain (server, intermediate, root) to identify a missing link or incorrect issuer causing trust errors in browsers.
- Security Audit and Compliance
- Verify that your certificates use modern signature algorithms (SHA-256 or higher) and sufficient key sizes (2048-bit RSA minimum or P-256 elliptic curve).
- Cryptography Education and Learning
- Explore the internal structure of an X.509 certificate visually to understand ASN.1 fields, OIDs, and how Public Key Infrastructure (PKI) works.
How to Use the Certificate Viewer
Paste your PEM-formatted certificate (starting with -----BEGIN CERTIFICATE----- and ending with -----END CERTIFICATE-----) into the text area, or click "Load sample" to test with a demo certificate.
Click "Parse certificate" to instantly decode the ASN.1/DER structure and display all information: subject, issuer, validity, algorithm, and public key.
Browse the results organized by section. You can copy the serial number or any other displayed information for your reports or technical documentation.
Frequently Asked Questions About PEM Certificates
- What is the difference between PEM and DER formats?
- PEM is a Base64 encoding of the binary DER format, wrapped with -----BEGIN/END CERTIFICATE----- headers. PEM is human-readable in a text editor and easier to share via email or paste into forms, while DER is the raw binary format used internally by systems.
- Is my certificate data sent to a server?
- No. Certificate parsing is performed entirely in your browser using a JavaScript ASN.1 decoder. No data is transmitted to any remote server, ensuring complete privacy of your certificates.
- What types of certificates can I analyze with this tool?
- This tool supports X.509 certificates in PEM format, including SSL/TLS server certificates, intermediate Certificate Authority (CA) certificates, and self-signed certificates. It decodes RSA, ECDSA (elliptic curve), and Ed25519 keys.
- How can I get the PEM certificate from my website?
- You can extract the certificate using the OpenSSL command: openssl s_client -connect mysite.com:443 -showcerts. You can also export it from your browser by clicking the padlock icon in the address bar and viewing the certificate details.
- What do the CN, O, and OU fields mean in a certificate subject?
- CN (Common Name) is the domain name or entity identified by the certificate. O (Organization) refers to the owning organization. OU (Organizational Unit) identifies the department or division within the organization. These fields make up the certificate's Distinguished Name (DN).