PEM Certificate Parser

Certificates

Processed locally in your browser using the Web Crypto API. Nothing is sent to any server.

How It Works

This tool parses PEM-encoded cryptographic files by stripping the base64 envelope, then decoding the underlying ASN.1/DER structure to extract human-readable metadata. No external libraries are used — the ASN.1 parser is implemented from scratch.

Supported Formats

  • X.509 Certificates (BEGIN CERTIFICATE) — subject, issuer, serial, validity dates, signature algorithm
  • PKCS#8 Private Keys (BEGIN PRIVATE KEY) — algorithm OID detection (RSA, EC)
  • SPKI Public Keys (BEGIN PUBLIC KEY) — algorithm identification
  • RSA Keys (BEGIN RSA PRIVATE/PUBLIC KEY) — key format detection

How PEM Parsing Works

  1. Strip the -----BEGIN ... ----- and -----END ... ----- headers
  2. Base64-decode the content to raw bytes (DER-encoded ASN.1)
  3. Parse the TLV (Tag-Length-Value) structure of the ASN.1 data
  4. Extract fields based on their position in the ASN.1 tree
  5. Decode OIDs to dotted notation, times to human-readable dates

Common Use Cases

  • Inspect SSL/TLS certificate details without OpenSSL
  • Verify certificate expiration dates and issuer information
  • Identify the algorithm and format of a cryptographic key
  • Debug certificate chain issues in web server configurations

Frequently Asked Questions

What is a PEM file?

PEM (Privacy-Enhanced Mail) is a base64-encoded container format for cryptographic keys and certificates. Despite its name, PEM is the standard format for SSL/TLS certificates, SSH keys, and code signing certificates.

What information can be extracted from a certificate?

An X.509 certificate contains the subject, issuer, serial number, validity period, public key, and signature algorithm. This tool extracts all these fields by parsing the ASN.1/DER structure.

Does this tool upload my certificate?

No. All parsing happens locally in your browser using JavaScript. Your certificate data is never sent to any server.

Privacy Note

This tool runs entirely in your browser. Your input is never uploaded, stored, or sent to any server.

Disclaimer: This tool is provided for educational and informational purposes only. The results do not constitute professional security advice. Use at your own discretion.