domain-check

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

Method	Command	Notes
Homebrew (macOS)	brew install domain-check	Easiest install for macOS users
Cargo (CLI)	cargo install domain-check	Works on all Rust-supported platforms
Cargo (MCP)	cargo install domain-check-mcp	MCP server for AI agents
GitHub Releases	Download binaries	CLI + MCP binaries for macOS, Linux, Windows

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 v1.2.1 — 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:

Preset	TLDs	Use case
startup	com, org, io, ai, tech, app, dev, xyz	Tech startups
popular	com, net, org, io, ai, app, dev, tech, me, co, xyz	General coverage
classic	com, net, org, info, biz	Traditional gTLDs
enterprise	com, org, net, info, biz, us	Business and government
tech	io, ai, app, dev, tech, cloud, software, + 5 more	Developer tools
creative	design, art, studio, media, photography, + 5 more	Artists and media
ecommerce	shop, store, market, sale, deals, + 3 more	Online retail
finance	finance, capital, fund, money, investments, + 4 more	Fintech
web	web, site, website, online, blog, page, + 3 more	Web services
trendy	xyz, online, site, top, icu, fun, space, + 6 more	New gTLDs
country	us, uk, de, fr, ca, au, br, in, nl	International

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 = "1.2.1"

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.