How to Check If a Domain Is Available (And Why Two Checkers Disagree)
Run the same domain through three availability checkers and you can get three answers. The reason is not a conspiracy, it is that most tools guess from DNS instead of asking the registry. Here is how to get a definitive answer.
September 21, 20267 min readDomain search · RDAP · Availability
Check one name or a whole list against each registry’s own data.
Check domain availabilityThe short answer. A domain is available only if the registry says it has no record of it. Ask the registry directly over RDAP and you get a definitive answer. Most checkers infer availability from DNS instead, which is fast, free and wrong often enough to matter.
You have probably had this happen. A name shows as available on one site, taken on another, and "premium, $2,400" on a third. All three are looking at the same domain.
Nothing shady is going on. They are using different methods, and only one of those methods is authoritative.
How to check a domain properly
1. Query the registry, not the internet. Every extension has a registry that holds the definitive list of registered names. Since 2025 the way to ask is RDAP, which returns structured JSON over HTTPS. If the registry has no record, you get HTTP 404 and the name is genuinely unregistered.
2. Treat DNS as a hint, never as proof. A missing A record does not mean a domain is free.
3. Check the price before you celebrate. Unregistered does not mean cheap. Registries reserve names and mark others as premium, sometimes at hundreds of times the standard rate.
4. Check the renewal, not the first year. A $1.99 name that renews at $19.99 is a $19.99 name. We compared what four registrars actually charge across five years.
Our checker routes every lookup through the IANA bootstrap registry to the authoritative RDAP server for that extension, and uses DNS only as a secondary signal. It never reports a name as available because DNS came back empty.
Why two checkers give different answers
DNS lookups produce false positives
This is the big one. A DNS query asks "where does this name point?" not "does this name exist in the registry?"
Plenty of registered domains have no DNS records at all:
- names bought and never configured, which is most of any investor's portfolio
- domains sitting in the grace period after expiry
- names held purely defensively, registered so a competitor cannot have them
Query DNS for any of those and you get nothing back. A checker that treats "no DNS response" as "available" will confidently offer you a domain somebody already owns. You find out at checkout.
WHOIS responses were never standardised
Before RDAP, tools parsed WHOIS text, and every registry invented its own format. Two tools parsing the same response with different assumptions reach different conclusions. This is precisely the problem RDAP was created to solve, and why ICANN dropped the WHOIS requirement in January 2025.
Caching
Availability results get cached. The gap between a name being registered and every tool reflecting it can be minutes or hours. For a name in demand, minutes matter.
Registrar inventory is not registry truth
A registrar's search box is a shop window. It can show a name as unavailable because it is genuinely registered, or because it is reserved, or because the registrar's own catalogue has not synced. The registry is the only source that knows for certain.
Does searching for a domain cause someone to register it?
This is the most persistent belief in the domain world, and it deserves a straight answer: there is no evidence it happens, and it has been formally tested.
The concern is real enough that ICANN's Security and Stability Advisory Committee published SAC 022 on domain name front running in October 2007. It noted that checking availability discloses interest in a name, and that queries could in principle be intercepted by browser plug-ins, toolbars or intermediaries.
ICANN then commissioned a study to find out whether it was actually occurring. Security researcher Benjamin Edelman ran three rounds of testing over ten months against leading registration and availability-checking sites. The result, published in 2009: more than 600 tests yielded no evidence of front running.
The myth survives because of a coincidence that feels like causation. Good names get registered constantly. If you search one on Monday and it is gone on Thursday, it is far more likely that somebody else had the same idea than that your search was sold.
The genuine risk SAC 022 identified was never the registrar. It was untrusted software in the middle: browser extensions, free WHOIS tools and toolbars that log what you type. That risk is addressed by not installing sketchy extensions, not by avoiding search boxes.
What "available" actually means
An unregistered domain still comes in several flavours, and only the first is what people expect.
| State | What it means | Can you get it? |
|---|---|---|
| Available | No registry record | Yes, at standard price |
| Premium | Registry has priced it above standard | Yes, often 10x to 1000x |
| Reserved | Registry withheld it from sale | No |
| Grace period | Recently expired, owner can still renew | Not yet |
| Redemption | Expired, recoverable by the owner for a fee | No, for about 30 days |
| Pending delete | Recovery window over, drop imminent | Soon, usually via a drop-catch service |
| Registered | Someone owns it | Only on the aftermarket |
The last three are why a name can read as "taken" today and be registrable in five weeks. We wrote about that timeline in What Happens When a Domain Expires.
Checking many names at once
Checking one domain is easy. Checking four hundred is where methods diverge sharply, because registries rate-limit RDAP and a naive tool will get throttled, time out, and quietly return "unknown" as "available".
If you are checking in bulk, the things that matter are:
- per-registry concurrency limits, so one extension's rate limit does not poison the whole run
- an explicit unknown state, because a timeout is not an answer
- no retry storms, which get your requests rejected harder
Our bulk checker streams results as they arrive and reports available, registered, unknown and error as four distinct outcomes rather than collapsing them into two.
Common questions
What is the most accurate way to check domain availability?
Query the authoritative registry over RDAP. It returns HTTP 404 when a name has no registry record and a structured JSON record when it does. No parsing, no inference, no guessing from DNS.
Why does a domain show as available but fail at checkout?
Usually because the checker inferred availability from a missing DNS record rather than asking the registry, or because the name is registry-reserved or premium-priced and the registrar's catalogue had not caught up.
Can someone steal a domain I searched for?
There is no evidence that registrars or availability checkers do this. ICANN commissioned a study that ran more than 600 tests over ten months and found no cases. The real exposure is untrusted browser extensions and toolbars that log what you type.
Does a domain with no website mean it is free?
No. Most registered domains have no website. Investors hold portfolios with no DNS configured, companies register names defensively, and expired domains sit in grace periods. A blank page is not a vacancy.
How long after a domain expires can I register it?
Usually around 75 days. There is a grace period of up to 45 days where the owner renews normally, then a redemption period of about 30 days where they can recover it for a fee, then a 5-day pending delete window, after which it drops.
Is WHOIS still reliable for availability?
Less so than it was. ICANN removed the requirement for registries and registrars to run WHOIS on port 43 in January 2025. Servers still answer in many cases, but nobody is obliged to keep them running. RDAP is the supported path.
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