Domain Check

Universal domain exploration engine: fast domain availability checks across the internet — as a CLI, Rust library, and MCP server for AI agents.

Quick Links: Installation | Quick Start | Use Cases | Output Formats | Presets | Configuration | Automation | Library | MCP Server | FAQ | Contributing

Why domain-check

• 1,200+ TLDs out of the box — IANA bootstrap loads the full registry automatically. No config needed. 34 hardcoded TLDs work offline as fallback.
• Dual-protocol engine — RDAP-first with automatic WHOIS fallback. IANA server discovery covers ~189 ccTLDs that lack RDAP (.it, .co, .eu, .jp). WHOIS is built in, so no system whois tool is needed on any platform.
• Fast — up to 100 concurrent checks, streaming results as they complete. 3.4 MB release binary.
• Domain generation — pattern expansion (\w=letter, \d=digit, ?=either), prefix/suffix permutations, and --dry-run to preview before checking.
• 11 curated presets — startup, tech, creative, finance, ecommerce, and more. Or define your own in config.
• For-sale detection — --for-sale reads RFC 10023 _for-sale records, so you can see when a registered domain is actually on the market (asking price and contact, sanitized, never auto-opened).
• Rich output — grouped pretty display, JSON, CSV. Registrar info, creation/expiration dates, and status codes with --info.
• CI and automation friendly — --json/--csv to stdout, --yes to skip prompts, --force for large runs, automatic non-TTY detection.
• Configurable — TOML config files, DC_* environment variables, custom presets, and clear precedence rules.
• Agent-native — MCP server exposes all tools to AI coding agents (Claude, Codex, Gemini, Cursor, VS Code Copilot, and any MCP client).
• CLI + library + MCP — same engine powers the CLI, domain-check-lib (Rust library), and domain-check-mcp (MCP server).

Installation

Quick Start

# Check a single domain
domain-check example.com

# Expand a base name across TLDs
domain-check mystartup -t com,org,io,dev

# Use a curated preset
domain-check myapp --preset startup --pretty

# Generate names with a pattern (preview only)
domain-check --pattern "app\d" -t com --dry-run

# Add prefixes and suffixes
domain-check myapp --prefix get,try --suffix hub,ly -t com,io

# Get registrar and date info
domain-check target.com --info

# Is a taken domain for sale? (RFC 10023)
domain-check example.nl --for-sale

# Check every known TLD
domain-check brand --all --batch

Pretty output:

domain-check v1.2.0 — Checking 8 domains
Preset: startup | Concurrency: 20

── Available (3) ──────────────────────────────
  rustcloud.org
  rustcloud.ai
  rustcloud.app

── Taken (5) ──────────────────────────────────
  rustcloud.com
  rustcloud.io
  rustcloud.tech
  rustcloud.dev
  rustcloud.xyz

8 domains in 0.8s  |  3 available  |  5 taken  |  0 unknown

Use Cases

# Startup naming — scan tech TLDs for your brand
domain-check coolname --preset startup --pretty

# Brand protection — audit every TLD for your trademark
domain-check mybrand --all --json > audit.json

# Pre-purchase validation — check registrar and expiry before buying
domain-check target.com --info

# Bulk pipeline — feed a list, export results
domain-check --file ideas.txt --preset tech --csv > results.csv

# Name generation — explore prefix/suffix combos
domain-check app --prefix get,my,try --suffix hub,ly -t com,io --dry-run

Output Formats

Default — one line per domain, colored status:

myapp.com TAKEN
myapp.io AVAILABLE
myapp.dev TAKEN

Pretty (--pretty) — grouped by status with summary:

── Available (1) ──────────────────────────────
  myapp.io

── Taken (2) ──────────────────────────────────
  myapp.com
  myapp.dev

3 domains in 0.4s  |  1 available  |  2 taken  |  0 unknown

JSON (--json) — structured, pipe to jq:

[
  {
    "domain": "myapp.com",
    "available": false,
    "method": "RDAP"
  },
  {
    "domain": "myapp.io",
    "available": true,
    "method": "RDAP"
  }
]

CSV (--csv) — import into spreadsheets or databases:

domain,status,method
myapp.com,TAKEN,RDAP
myapp.io,AVAILABLE,RDAP

Info (--info) — registrar, dates, and status codes:

myapp.com TAKEN
  Registrar: Example Registrar, Inc.
  Created: 2015-03-12  Expires: 2026-03-12
  Status: clientTransferProhibited

Full reference: docs/CLI.md

Smart Presets

11 built-in presets covering common domains strategies:

domain-check --list-presets                          # See all presets with full TLD lists
domain-check mybrand --preset creative --pretty      # Use a preset

Define custom presets in your config file:

[custom_presets]
my_stack = ["com", "io", "dev", "app"]

Configuration

Create domain-check.toml in your project directory:

[defaults]
concurrency = 25
preset = "startup"
pretty = true
timeout = "8s"
bootstrap = true
for_sale = false        # set true to always check registered domains for RFC 10023 for-sale records

[custom_presets]
my_startup = ["com", "io", "ai", "dev", "app"]

[generation]
prefixes = ["get", "my"]
suffixes = ["hub", "ly"]

Config lookup order: ./domain-check.toml > ~/.domain-check.toml > ~/.config/domain-check/config.toml

Common environment variables:

DC_CONCURRENCY=50    DC_PRESET=startup    DC_TLD=com,io,dev
DC_PRETTY=true       DC_TIMEOUT=10s       DC_BOOTSTRAP=true
DC_PREFIX=get,my     DC_SUFFIX=hub,ly     DC_FILE=domains.txt
DC_FOR_SALE=true     DC_DNS_SERVER=1.1.1.1

Automation & CI

# Non-interactive structured output
domain-check --file required-domains.txt --json

# Pipe to jq
domain-check --pattern "app\d" -t com --yes --json | jq '.[] | select(.available==true)'

# Stream live results for long runs
domain-check --file large-list.txt --concurrency 75 --streaming

# Large batch with no prompts
domain-check --file huge-list.txt --all --force --yes --csv > results.csv

CI-friendly behavior:

• --yes / --force skip all confirmation prompts
• Non-TTY environments (piped, CI) never prompt — scripts are never blocked
• Spinner writes to stderr; stdout stays clean for piping
• --no-bootstrap for deterministic, offline-safe checks against 34 hardcoded TLDs

Automation guide: docs/AUTOMATION.md

Library

Use domain-check-lib directly in Rust projects:

[dependencies]
domain-check-lib = "1.2.0"

use domain_check_lib::DomainChecker;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let checker = DomainChecker::new();
    let result = checker.check_domain("example.com").await?;
    println!("{} -> {:?}", result.domain, result.available);
    Ok(())
}

Library docs: domain-check-lib/README.md | docs.rs

MCP Server

domain-check-mcp exposes domain checking as tools for AI coding agents via the Model Context Protocol. Works with any MCP-compatible client.

# Install
cargo install domain-check-mcp

# Add to your agent (Claude Code example — works similarly for Codex, Gemini CLI, etc.)
claude mcp add domain-check -- domain-check-mcp

6 tools available: check_domain, check_domains, check_with_preset, generate_names, list_presets, domain_info.

Then ask your agent naturally: "Is coolstartup.com available?" or "Check mybrand across the startup preset".

The check tools take an optional check_for_sale parameter, and domain_info always includes RFC 10023 for-sale info when the holder publishes it. Responses mark that data as unverified and report failed lookups in for_sale_errors. Set DC_DNS_SERVER in the MCP client's env to choose the DNS server.

Supports: Claude Code, Claude Desktop, VS Code Copilot, Cursor, Windsurf, JetBrains, OpenAI Codex CLI, Gemini CLI, and any MCP stdio client.

Full setup: domain-check-mcp/README.md

Reliability Notes

• Domain status is network- and registry-dependent. Temporary errors can produce UNKNOWN states.
• WHOIS output is less standardized than RDAP. domain-check reads the reply formats of 40+ registries and answers UNKNOWN rather than guess. Some registries (.es, .gr, .vn, …) offer no public WHOIS, so their domains show UNKNOWN when RDAP can't answer.
• For repeatable CI workflows, pin behavior with explicit flags (--batch, --json, --no-bootstrap, --concurrency).

Troubleshooting and expected edge cases: docs/FAQ.md

Project Docs

• CLI reference: docs/CLI.md
• Library: domain-check-lib/README.md | docs.rs
• MCP server: domain-check-mcp/README.md
• Examples and workflows: docs/EXAMPLES.md
• Automation usage: docs/AUTOMATION.md
• FAQ: docs/FAQ.md
• Changelog: CHANGELOG.md
• Contributing: CONTRIBUTING.md
• Security policy: SECURITY.md

License

Licensed under either of

• Apache License, Version 2.0
• MIT License

at your option.