Peek509

Peek509 is a lightweight VS Code extension that lets you decode and inspect X.509 certificates directly from .pem or .crt files. Right-click a certificate file or run the command from the palette to instantly view its contents in a clean, human-readable format. No terminal commands required.

Features

Certificate Decoding

• Decode .pem and .crt files via:

  • Right-click in Explorer
  • Command Palette (with file picker fallback)

• Supports manual ASN.1 parsing using asn1js and pkijs

• Handles RSA and ECDSA public keys, with future extensibility for EdDSA

Webview Certificate Viewer (New in 1.3.0)

• Rich HTML UI powered by TailwindCSS
• Light/Dark theme support
• Collapsible sections for clean navigation
• Copy‑to‑clipboard buttons for long fields:
• SHA‑256 fingerprint
• RSA modulus
• EC public key
• SKI / AKI
• Other long extension values
• HTML formatters for supported X.509 extensions

Text Based Viewer

• Optional plain‑text rendering mode (peek509.renderMode)
• Clean indentation and aligned formatting
• No save prompt — output opens in a virtual document

Parsed Certificate Fields

• Subject and Issuer details (with OID mapping)

• Validity period

• Serial number

• SHA‑256 fingerprint

• Public key details (RSA/ECDSA)

• Parsed extensions:

  • keyUsage
  • extendedKeyUsage
  • subjectKeyIdentifier
  • authorityKeyIdentifier
  • basicConstraints
  • subjectAltName
  • Additional extensions where supported

Usage

Option 1: Right-click

• Open your project in VS Code.
• Right-click any .pem or .crt file in the Explorer.
• Select "Peek509: Decode x509 Certificate".
• View the decoded certificate in the Webview or text viewer (based on settings)

Option 2: Command Palette

• Open the Command Palette (Ctrl+Shift+P or Cmd+Shift+P).
• Run "Peek509: Decode x509 Certificate".
• Select a certificate file from anywhere on your system.
• The decoded output will be displayed immediately

Configuration

Installation

Search for Peek509 in the Visual Studio Marketplace or install via the Extensions panel in VS Code.

Roadmap

Planned enhancements for future versions:

• Multi‑certificate file support
• CSR and CRL decoding
• Decode PEM strings directly from highlighted text
• Certificate/key generation (RSA/ECDSA)
• Signature verification and trust chain visualization
• Export decoded certificate as JSON or PEM
• Dark‑mode auto‑detection
• Inline ASN.1 tree view for raw DER

License

MIT License — see LICENSE for details.