Overview

Domain Availability Checker sends each entered domain to an external lookup service. Fast Mode uses Cloudflare public DNS-over-HTTPS service, while Detailed Mode queries rdap.org for registration information such as registrar details and expiry dates.

How to Use

Choose Check Method
Select Fast Mode (DNS) to send domains to Cloudflare public DNS-over-HTTPS service. Choose Detailed Mode (RDAP) to send domains to rdap.org for registration information including registrar, creation date, and expiry date.
Enter Domain Names
Paste your domain list with one domain per line, or separate them with commas or semicolons. The tool will automatically parse and clean the input. You can include or exclude the "www." prefix - it will be handled correctly.
Review Results
Results show each domain's status (Available, Registered, or Error), the check method used, and additional details. For WHOIS checks, you'll see registrar information and important dates when available.

Use Cases

Domain Name Research

Quickly check availability of multiple domain name candidates when brainstorming names for your new project, business, or website. Save time by checking dozens of domains at once.

Domain Portfolio Management

Monitor the registration status of domains in your watchlist. Check if expired domains have become available or verify the status of domains you're interested in acquiring.

Competitor Analysis

Research domain portfolios of competitors or check if related domain variations are registered. Useful for brand protection and market research.

Bulk Domain Validation

Validate large lists of domains for marketing campaigns, SEO research, or data cleanup. Identify which domains in your database are still active.

Frequently Asked Questions

What's the difference between Fast Mode and Detailed Mode?

Fast Mode (DNS) checks if a domain has DNS records configured, which usually indicates registration. It's very fast but may occasionally show false positives for registered domains without DNS. Detailed Mode (WHOIS) queries the domain registry directly for accurate registration information, but it's slower and may have rate limits.

Why does Fast Mode show a domain as available when it's actually registered?

Fast Mode checks for DNS records, not registration status. A registered domain without configured DNS records will appear as available. For accurate results, use Detailed Mode (WHOIS) which checks the actual domain registry.

How many domains can I check at once?

You can check multiple domains in one batch. However, to avoid rate limiting, there's a small delay between checks (200ms for DNS, 1000ms for WHOIS). Checking many domains with WHOIS may take several minutes.

Does this tool support all domain extensions?

The tool supports most common domain extensions (.com, .net, .org, country codes, etc.). However, some newer or specialized TLDs may have limited WHOIS data availability. DNS checking works for all domains with standard DNS configuration.

Is my domain search private?

Entered domains are sent to Cloudflare public DNS-over-HTTPS service in Fast Mode or rdap.org in Detailed Mode. These providers receive and may log the query under their own policies; ToolCLI does not intentionally persist the domain list.

Concept Notes

Domain lifecycle realities

WHOIS and DNS data propagate with lag, so availability checks can differ across registrars and resolvers. Before go-live, align A/AAAA, CNAME, and TXT (SPF/DKIM) records and set sane TTLs—stray legacy records or mismatched caching often cause intermittent resolution or mail deliverability issues.