Domain Name Availability API for Real-Time Registration Checks
Check if a domain name is available or already registered in real time. Powered by live WHOIS data, covering all major TLDs and ccTLDs. Structured JSON response, sub-200ms latency, same API key as all WhoisJSON services.
Check Domain Availability Now
Enter any domain name to see its registration status in real time.
Simple, Fast, Accurate
One API call returns a clear boolean result backed by live WHOIS data — not cached guesswork.
Send a Request
Pass any domain name to our endpoint. We accept all TLDs and ccTLDs — .com, .io, .de, .co.uk and 1,500+ more.
Real-Time WHOIS Check
We query live WHOIS servers to determine registration status. No stale databases, no guessing — just accurate, real-time results.
Get Instant Result
Receive a clean JSON response with the domain name and a boolean available field. Integrate directly into your UI or backend logic.
Built for Scale & Accuracy
Sub-200ms Response
Optimized for speed. Results come back faster than a page load — perfect for search-as-you-type interfaces.
1,500+ Extensions
All major gTLDs, ccTLDs, and new extensions. From .com to .xyz to .co.jp.
Registrar-Level Accuracy
Powered by live WHOIS/RDAP queries — the same data source registrars use to verify availability.
High Throughput
Loop over your domain lists at high speed. Rate limits scale from 20 to 900 req/min depending on yourplan.
Who Uses Domain Availability Data?
Domain Registrars & Marketplaces
Power your domain search bar with real-time availability checks. Show customers which domains are available before they commit — reducing failed registrations and improving conversion rates.
Brand Protection Teams
Monitor when brand-related domains become available. Combine with WHOIS lookups to verify ownership and with monitoring alerts to get notified of changes to competitor domains.
Domain Investors
Scan expiring domain lists and check availability the moment they drop. Automate your acquisition pipeline with bulk checks and WHOIS data for valuation research.
SaaS & Website Builders
Let users search for and register custom domains directly in your app. Check availability in real time and validate DNS configuration and SSL certificates after provisioning.
One Endpoint, One Boolean
The simplest endpoint on the platform. Pass a domain, get a clear answer: available or taken.
Authentication: Authorization: TOKEN=YOUR_API_KEY
Response: JSON (default) or XML
// Domain available
{
"domain": "my-new-startup.com",
"available": true
}
// Domain taken
{
"domain": "google.com",
"available": false
}
What Is a Domain Availability API?
A domain availability API lets you programmatically check whether a domain name is available for registration. Instead of visiting a registrar website and typing domain names one by one, you send an HTTP request and get an instant boolean response. WhoisJSON's Domain Availability API is powered by live WHOIS and RDAP queries — the same authoritative data source that registrars themselves rely on. This means you get registrar-level accuracy with sub-200ms response times, covering over 1,500 TLDs and country-code extensions.
Part of the WhoisJSON Unified Platform
Domain availability checking is one of six services accessible with your WhoisJSON API key. The same token also powers WHOIS lookups for full registration details, DNS record resolution for infrastructure analysis, SSL certificate validation for security checks, subdomain discovery for DNS enumeration, and domain monitoring with real-time alerts. This unified approach lets you combine availability data with WHOIS ownership info, DNS configurations, and SSL status in a single workflow — no extra keys, no extra providers.
Scalable from Hobby Projects to Enterprise
The free plan includes 1,000 requests per month shared across all endpoints — plenty for testing, prototyping, and small-scale projects. When you need more throughput, our paid plans offer up to unlimited requests with rate limits of 900 req/min. Responses are cached briefly for performance, and you can bypass the cache with_forceRefresh=1 when freshness matters. Explore the API documentation or check our FAQ for integration details.
Domain Availability API vs WHOIS API
Availability checks and WHOIS lookups answer different questions. Use the availability endpoint when you need a registration decision, and the WHOIS endpoint when you need ownership and lifecycle details.
| API | Main question answered | Response data | Best for |
|---|---|---|---|
| Domain Availability API | Can this domain be registered? | available status: true, false, or unknown | Domain search, registrar-style checkout, SaaS onboarding, startup name validation, bulk availability checks |
| WHOIS API | Who owns this domain and when does it expire? | Registrar, registration dates, expiration date, nameservers, status codes, registrant data when public | Domain research, portfolio audits, brand protection, cybersecurity enrichment, ownership verification |
For acquisition, brand protection, or marketplace workflows, combine both endpoints: first check whether a domain is available, then enrich registered domains with WHOIS data.
Frequently Asked Questions about the Domain Availability API
available boolean field: true if the domain is free to register, false if it is already taken. unknown status means the API could not definitively determine whether the domain is free or taken — this can occur for unsupported TLDs, WHOIS server timeouts, or non-standard registry responses. It does not mean the domain is available..de, .co.uk, .fr, and .co.jp. Coverage depends on the underlying WHOIS or RDAP behavior for each registry.Start Checking Domain Availability Today
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