sslmon

April 25, 2026 · View on GitHub

A command-line tool for querying domain registration info (WHOIS/RDAP) and SSL certificate details. Fast, zero-dependency, cross-platform single binary.

Quick Start

Download

Download the latest binary from Releases, or build from source:

git clone https://github.com/firesh/sslmon-cli.git
cd sslmon-cli
make build        # local binary → ./sslmon
make build-all    # cross-compile all platforms → dist/

Usage

# Query domain registration info
sslmon domain sslmon.dev

# Check SSL certificate
sslmon ssl sslmon.dev
sslmon ssl sslmon.dev --port 8443

Commands

`sslmon domain <domain>`

Query domain registration, expiration, registrar, and status via RDAP (with WHOIS fallback).

Output: JSON object:

domain — Queried domain
registrationDate — Registration date (ISO 8601)
expirationDate — Expiration date (ISO 8601)
registrar — Registrar name
registrant — Registrant info (when available)
status — Domain status
daysUntilExpiry — Days until expiration

`sslmon ssl <domain> [--port 443]`

Check SSL certificate validity, issuer, and expiration.

Output: JSON object:

domain — Queried domain
validFrom — Certificate valid from (ISO 8601)
validTo — Certificate valid to (ISO 8601)
issuer — Certificate issuer CN
subject — Certificate subject CN
isValid — Whether the certificate is currently valid
daysUntilExpiry — Days until expiration

Examples

$ sslmon domain sslmon.dev
{
  "domain": "sslmon.dev",
  "registrationDate": "2023-05-08T10:04:19Z",
  "expirationDate": "2027-05-08T10:04:19Z",
  "registrar": "CloudFlare, Inc.",
  "status": "client transfer prohibited",
  "daysUntilExpiry": 378
}

$ sslmon ssl sslmon.dev
{
  "domain": "sslmon.dev",
  "validFrom": "2026-02-01T00:00:00Z",
  "validTo": "2026-06-01T23:59:59Z",
  "issuer": "R12",
  "subject": "sslmon.dev",
  "isValid": true,
  "daysUntilExpiry": 32
}

Supported Platforms

Platform	Arch
Linux	amd64, arm64
macOS	amd64, arm64
Windows	amd64

sslmon-mcp — MCP server for the same domain/SSL queries, integrates directly with AI tools like Claude, Gemini, and Qwen.

License

MIT