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 systemwhoistool 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-runto preview before checking. - 11 curated presets —
startup,tech,creative,finance,ecommerce, and more. Or define your own in config. - For-sale detection —
--for-salereads RFC 10023_for-salerecords, 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/--csvto stdout,--yesto skip prompts,--forcefor 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), anddomain-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 v1.2.1 — 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:
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/--forceskip all confirmation prompts- Non-TTY environments (piped, CI) never prompt — scripts are never blocked
- Spinner writes to stderr; stdout stays clean for piping
--no-bootstrapfor 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
UNKNOWNstates. - WHOIS output is less standardized than RDAP. domain-check reads the reply formats of 40+ registries and answers
UNKNOWNrather than guess. Some registries (.es,.gr,.vn, …) offer no public WHOIS, so their domains showUNKNOWNwhen 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
at your option.
