domain-checker

A lightweight CLI tool to check domain name availability using DNS resolution and whois lookups. Zero external dependencies.

Features

• Dual-check strategy — DNS first (fast), whois as fallback (accurate)
• Configurable TLDs — check any combination of extensions
• File input — pass a .txt file with one name per line
• JSON & CSV export — pipe results into other tools or save them
• --quiet mode — only print available domains
• No external npm packages — uses only Node.js built-ins + system whois

Requirements

| Dependency | Notes | |---|---| | Node.js ≥ 14 | nodejs.org | | whois CLI | Pre-installed on macOS and most Linux distros |

Windows: whois is not bundled. Install it via Sysinternals or use WSL.

Installation

Use instantly with npx (no install needed)

npx @cmrabdu/domain-checker myapp mysite

Install globally

npm install -g @cmrabdu/domain-checker
domain-checker myapp mysite

Run from source

git clone https://github.com/cmrabdu/domain-chekcer.git
cd domain-chekcer
node domain-checker.js myapp mysite

Usage

domain-checker [options] [names...]

Arguments

| Argument | Description | |---|---| | names | One or more base names to check (e.g. myapp coolsite) |

Options

| Option | Default | Description | |---|---|---| | -e, --extensions <list> | .com,.io,.app,.org | Comma-separated TLD list | | -f, --file <path> | — | Text file with one base name per line | | -o, --output <path> | — | Save results to a .json or .csv file | | -d, --delay <ms> | 350 | Delay between checks (ms) | | --json | — | Print results as JSON (machine-readable) | | -q, --quiet | — | Only print available domains | | -v, --version | — | Print version | | -h, --help | — | Show help |

Examples

Check a few names across default TLDs

node domain-checker.js myapp coolsite

Check specific extensions

node domain-checker.js -e .com,.io,.fr myapp

Read names from a file

node domain-checker.js -f examples/domains.example.txt

Export results to JSON

node domain-checker.js myapp -e .com,.io -o results.json

Export results to CSV

node domain-checker.js myapp -e .com,.io -o results.csv

Only show available domains (quiet mode)

node domain-checker.js -f examples/domains.example.txt -q

JSON output (great for scripting)

node domain-checker.js myapp --json | jq '.[] | select(.available == true)'

Input file format

Create a plain text file with one base name per line. Lines starting with # are treated as comments.

# examples/my-domains.txt
myapp
coolsite
awesomeproject

Then run:

node domain-checker.js -f my-domains.txt -e .com,.io

Sample output

Domain Checker  DNS + whois · 8 domain(s)

  myapp.com                     ✗  taken  (dns:A)
  myapp.io                      ✓  available
  myapp.app                     ✗  taken  (whois:record)
  myapp.org                     ✗  taken  (dns:NS)
  coolsite.com                  ✗  taken  (dns:A)
  coolsite.io                   ✓  available
  coolsite.app                  ✓  available
  coolsite.org                  ✗  taken  (dns:A)

──────────────────────────────────────────────────

Available (3)
  myapp.io
  coolsite.io
  coolsite.app

Taken: 5

──────────────────────────────────────────────────

Tip: Always confirm on namecheap.com or porkbun.com before purchasing.

How it works

The script uses a two-step strategy:

1. DNS check — Queries A, NS, and MX records. If any resolves, the domain is taken.
   This is fast and reliable for registered domains.

2. whois check — Runs the system whois command on the domain.
   The output is parsed for known "free" and "taken" signals.
   Some TLD registries (e.g. .app, .io) return only TLD-level data, so the script falls back to the DNS result in ambiguous cases.

Results marked dns-clean+whois-tld mean DNS returned nothing and whois only showed TLD-level info — the domain is very likely available, but confirming with a registrar is recommended.

Result schema (JSON)

Each result object looks like this:

{
  "domain": "myapp.io",
  "available": true,
  "method": "whois:free"
}

| Field | Type | Description | |---|---|---| | domain | string | Full domain name checked | | available | true / false / null | Availability result (null = timeout/undetermined) | | method | string | How the result was determined |

Method values

| Value | Meaning | |---|---| | dns:A / dns:NS / dns:MX | Taken — DNS record found | | whois:record | Taken — domain record found in whois | | whois:registrar | Taken — registrar info found in whois | | whois:free | Available — whois returned a "free" signal | | dns-clean+whois-tld | Likely available — no DNS, no registrar info | | timeout | Undetermined — whois timed out |

Contributing

Contributions are welcome! Feel free to open an issue or submit a pull request.

1. Fork the repo
2. Create a feature branch: git checkout -b feature/my-feature
3. Commit your changes: git commit -m 'feat: add something'
4. Push: git push origin feature/my-feature
5. Open a Pull Request

License

MIT © cmrabdu