Two domain search tools will happily give you two different answers about the same name on the same day. Neither is necessarily lying. They are asking different systems different questions, and each of those systems knows something the others do not.
This guide explains what actually happens behind an availability check: which source is authoritative, why some extensions cannot give you a straight answer, why an available name can still cost hundreds of dollars at checkout, and how to read a result so you know how much to trust it.
What this guide covers
- 01There are four different sources, and they disagree
- 02RDAP is the registry's own answer
- 03DNS answers a different question entirely
- 04Not every extension will give you a straight answer
- 05Available does not mean standard price
- 06How to read a result like a professional
- 07Checking hundreds of names without getting blocked
01There are four different sources, and they disagree
"Is this domain available?" is not one question. It is four, answered by four different systems with different coverage, different freshness and different incentives.
| Source | The question it answers | Authoritative? | Blind spot |
|---|---|---|---|
| RDAP | Does the registry hold a record for this domain? | Yes | Not published by every country registry; can rate-limit |
| WHOIS | Same question, older protocol | Mostly | Unstructured text, inconsistent formats, being retired |
| DNS | Is this name resolving right now? | No | Registered names with no records look like nothing |
| Registrar inventory | Will this seller sell it to you, and for how much? | For price, yes | Cached lists go stale; inventory varies by seller |
| Zone files | Was it registered as of the last publication? | No | Published on a delay, usually daily |
02RDAP is the registry's own answer
RDAP — the Registration Data Access Protocol — is the modern replacement for WHOIS. Every registry that supports it publishes a machine-readable endpoint, and IANA maintains a bootstrap file that maps each extension to the right endpoint. Ask that endpoint about a domain and you get one of two useful answers.
404 Not Found
The registry has no record for this name. That is as close to a definitive "available" as exists outside a registrar's own checkout system.
200 OK with a record
The domain is registered. The response also carries the registrar, creation and expiry dates, status codes and nameservers — everything a WHOIS lookup used to give you, in structured form.
429 or 503
You have been rate-limited or the service is down. This is not an availability answer and should never be displayed as one.
03DNS answers a different question entirely
A DNS lookup does not ask whether a domain is registered. It asks whether the name resolves right now. Those two facts come apart constantly, in both directions, which is exactly why combining them is worthwhile.
| Registry record | DNS resolves | What it means |
|---|---|---|
| No | No | Genuinely available — register it |
| Yes | Yes | Registered and in active use |
| Yes | No | Registered but parked or dormant; possibly for sale |
| No record returned | Yes | Registry data is missing or stale — treat as taken |
That last row is the important one. If a name is serving a live website, it is registered, no matter what an availability list says. A tool that only reads a cached list will confidently offer you a domain that has had a business on it for six years.
The registry says what is owned. DNS says what is alive. You want both before you get excited.
04Not every extension will give you a straight answer
There are well over 1,500 extensions in the root zone, and their operators range from global registries with industrial-grade infrastructure to small national bodies running a service on a modest budget. Coverage varies accordingly.
No public RDAP service
Several country-code registries publish nothing machine-readable, or only a web form with a CAPTCHA. For those, the only honest answer is "check at the registrar".
Aggressive rate limits
Some registries allow a handful of queries per minute per address. A tool checking hundreds of extensions at once has to back off or it gets blocked.
Restricted registration
Some extensions are technically available but legally restricted — you may need a local presence, a professional credential or an accredited membership.
Reserved and blocked names
Registries reserve categories of names: one and two-character labels, geographic terms, and industry-specific words. These read as unregistered but cannot be bought normally.
05Available does not mean standard price
Availability data and pricing data are separate systems. A registry can flag any individual name as premium and assign it a price far above the standard rate for that extension. The name is genuinely unregistered, so it correctly shows as available — and then costs several hundred dollars at checkout.
- 1
Check availability first
Establish that nobody holds the name. This is the free, fast part, and it eliminates most candidates.
- 2
Then check the price at a registrar
Only the registrar knows the actual cost, because only the registrar sees the registry's premium tier for that specific name.
- 3
Look at renewal, not just year one
Registry premiums frequently recur annually. A promotional first year can hide a renewal that is ten times higher.
- 4
Confirm before you commit the brand
Do not design a logo around a name whose price you have not seen at checkout.
06How to read a result like a professional
Once you know what feeds a result, you can calibrate how much to trust it. Here is the practical hierarchy, from most to least reliable.
| Signal | Confidence | Action |
|---|---|---|
| Registry 404 plus no DNS | Very high | Register with confidence |
| Registry 404, DNS resolves | Low | Investigate before buying |
| Registry record present | Very high | Taken — move on or approach the owner |
| No RDAP for this extension | Unknown | Verify at a registrar |
| Cached list only | Medium | Re-verify live before paying |
See the sources for yourself
Check any name and the result shows registry data, DNS status and live site detection side by side — so you can see why the answer is what it is.
Live registry data across 300+ extensions. Good names get snapped up fast.
Two tools disagreeing is rarely a bug. It is usually one tool reading a daily zone file and another asking the registry in real time. Once you know which one you are looking at, the disagreement stops being confusing and starts being informative.
07Checking hundreds of names without getting blocked
Once you move from checking one name to sweeping a shortlist across dozens of extensions, availability checking becomes an engineering problem rather than a lookup. Registries publish rate limits, and a naive tool that fires a thousand simultaneous requests will get throttled, start receiving errors, and then display those errors as if they were answers.
Concurrency has to be bounded
A small pool of parallel requests per registry keeps you inside published limits while still returning a full sweep in seconds rather than minutes.
Failures must be distinguishable from answers
A timeout is not an availability result. Surfacing it as "available" is the single most damaging bug an availability tool can ship.
Priority ordering matters more than raw speed
The extension you typed and the handful you actually care about should resolve first, so you get a usable answer before the long tail finishes.
Caching has to be short
Availability changes by the minute in popular extensions. A cache measured in hours will hand you names that were registered this morning.
The same discipline applies to how results are presented. A responsible tool distinguishes four states — available, taken, premium and unknown — and never collapses the fourth into one of the first three. Any interface that only offers a green tick or a red cross is hiding information you need.
Sweep a whole shortlist at once
Paste your candidate names and get a full availability matrix across the extensions you choose, with live registry data behind every cell.
Live registry data across 300+ extensions. Good names get snapped up fast.
Frequently asked
Is WHOIS still accurate?
WHOIS still works for many extensions and returns broadly the same facts, but it is unstructured text with inconsistent formatting between registries. Registries are steadily migrating to RDAP, which returns structured JSON and is far easier to parse reliably.
Why does one tool say available and another says taken?
Usually because they use different sources. A tool reading a cached zone file or a registrar's inventory list can be up to a day behind a live registry query, and a name that is registered but not resolving in DNS will look free to anything that only checks DNS.
Can a search reveal my idea to domain squatters?
Front-running by search tools is rare among reputable services and generally prohibited by registry policy, but the safest practice is to register a name promptly once you have decided, rather than searching it repeatedly over several weeks.
Does an expired domain become available immediately?
No. Most extensions run a grace period of roughly thirty days where the owner can renew, followed by a redemption period, then a short pending-delete window. Only after that does the name return to general availability.
Put it into practice
Type a name and see live registry availability across hundreds of extensions in one go — then register it in a couple of clicks.
Free. No sign-up. Good names get snapped up fast.