Bulk WHOIS sounds simple until you actually try it. Most registry WHOIS servers throttle you at 5-20 queries per minute. The bulk APIs (Whoxy, ViewDNS, JsonWHOIS) cost $5-50/month and start at 500-2,000 lookups. If you just need to check ownership data on a list of 200-500 domains for a one-time audit, here's the friction-free path.
Bulk WHOIS — Free, No API Key
Bulk Domain Checker runs entirely in your browser. No account, no upload, no watermark.
Add to Chrome — FreeWhy bulk WHOIS is harder than bulk DNS
DNS lookups are cheap and effectively unlimited — every browser does dozens per minute. WHOIS is different. It runs on a separate protocol (port 43) that registries actively throttle. Hit the .com WHOIS server with 50 requests/minute from one IP and you'll get a temporary block. Hit it with 500/minute and you'll get a multi-day block.
The legitimate bulk WHOIS providers (Whoxy, MarkMonitor, DomainTools) pay registries for unthrottled feeds. That's why their APIs cost real money.
How the extension dodges the rate limit
Three tactics, none of them sketchy:
- DNS-first: 80% of "is this domain registered" questions can be answered by DNS A-record presence. WHOIS is only invoked when DNS is ambiguous (domain present but parked, or NXDOMAIN that might be cached).
- Pacing: requests are spaced at ~1 per 1.5 seconds, well under registry throttle thresholds.
- Per-TLD routing: different TLDs have different WHOIS servers; the extension queries the correct one rather than relying on a single fallback.
Net effect: a 500-domain bulk WHOIS finishes in roughly 12-15 minutes without tripping any block.
When you really do need a paid API
The extension is the right tool for one-off audits, name research, and a few hundred lookups per day. It's not the right tool for:
- Continuous brand-monitoring of 50,000+ domains daily — pay for an API.
- Granular WHOIS history (who owned this domain in 2018) — needs DomainTools or Whoxy historical.
- Reseller-level features like bulk DNS reports, MX scans, SSL fingerprinting — needs ViewDNS Pro or similar.
Output format and what you get back
For each domain the extension shows: registration status (available / registered / parked / unclear), creation date if WHOIS exposed it, expiry date if available, registrar name, and current name servers. Export to CSV for spreadsheet work.
What you don't get back from bulk WHOIS: registrant contact details. Since GDPR (2018) and the .com WHOIS data redaction (2019), individual registrant emails are mostly hidden behind privacy services. This is true regardless of what tool you use.
Common error: "WHOIS server timeout"
If you see WHOIS timeouts on a particular TLD, it usually means the registry is temporarily overloaded (common during ICANN policy events or registrar migrations). The extension will mark these rows as "unclear" rather than guessing. Re-run just the unclear rows 30 minutes later and they almost always resolve.
How Bulk WHOIS Lookup Without an API Key — Tools Compared
| Tool | Cost | Setup time | Bulk cap | API key needed | Includes registration date |
|---|---|---|---|---|---|
| Bulk Domain Checker (extension) | Free | 30 sec | No cap (paced) | No | Yes |
| Whoxy API | $0.0025-0.025/lookup | 15 min (signup + key) | Plan-based | Yes | Yes |
| ViewDNS API | $10-50/mo | 15 min | Plan-based | Yes | Yes |
| DomainTools | $99+/mo | 60 min (verification) | Unlimited | Yes | Yes (with history) |
| Manual whois CLI | Free | 0 min (built into Linux/Mac) | Throttled fast | No | Yes |
Get It Done in Under a Minute
Install the free Chrome extension and process your PDFs locally. Works on Windows, Mac, Linux, and Chromebook.
Add Bulk Domain Checker to ChromeRelated Guides
- How to Check 1,000+ Domains at Once
- Domain Availability Without Rate Limits
- How to Find Expired Domains in Bulk
- Brand Monitoring with Bulk Domain Checks
Frequently Asked Questions
Why do I need a tool for WHOIS — isn't the command line free?
For a handful of domains, the whois CLI is fine. For a list of 200+, the registry throttle will block you within a few minutes. The extension paces requests and routes per TLD to avoid that.
Will the extension show registrant email?
No, because most registrar WHOIS responses now redact registrant contact details under GDPR. No tool can reliably show this for non-corporate registrants.
How long does 500 domains take?
Roughly 12-15 minutes with the DNS-first + paced WHOIS strategy. Pure WHOIS-only would be 60+ minutes due to registry throttles.
Does it work for ccTLDs like .de or .uk?
Yes for most. A few country registries (.io, .ws) throttle aggressively and may need smaller batches.
Can I export results?
Pro plan exports CSV with all WHOIS fields. Free plan shows results in-extension.
