Bulk domain extension checker: many names across .com, .io, .ai and more
In short: Paste a shortlist of names, pick the extensions, and get a grid: every name in every extension marked Likely available, Registered or Unknown from the registry itself. Limit: Likely available isn't a guarantee: premium, reserved and blocked names can have no public record.
A bulk domain extension checker tries several names across several extensions at once. Paste up to 25 names, pick up to 10 extensions such as .com, .io, .ai and .co, and every pairing is checked at its registry's RDAP server and in DNS: Likely available, Registered or Unknown. Up to 100 pairings a run, or 500 after a free Google sign-in. CSV out.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Each name is checked in .com, .net, .org, .io, .co, .ai, .app, .dev. Pairings count towards the run limit: 10 names in 8 extensions is 80.
Sample result
northwind is registered in .com and .io; the .ai registry has no record and no nameservers for it.
- Name
- northwind
- .com
- Registered
- .io
- Registered
What this means for you
Likely available still needs the registrar's checkout: premium and reserved names can look free.
- Up to 25 names x 10 extensions
- Answers from each registry, not a reseller
- Unknown never shown as available
- Grid view and CSV
- .com
- .io
- .ai
By SimpleVerifier Team · Last updated
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Buying domains to send cold email from?
- New sending domains need warm-up, and every bounce counts against them from the first day. Before the first campaign, upload the recipient list at /verify to remove addresses that would bounce.
- The first 100 email checks are free with a Google sign-in, no card. For a list of full domains rather than names, use the bulk domain availability checker.
How do I check many domain names across many extensions?
- Paste names, one per line: words like northwind or full domains like northwind.com (only the name part is used).
- Pick the extensions, up to 10, or type your own. Each name is paired with each extension: 10 names in 8 extensions is 80 checks.
- Press Check names. Up to 100 pairings a run without an account, or 500 after a free Google sign-in, 20 pairings a request.
- Read the grid: Likely available, Registered (with the registrar and expiry when the registry shows them) or Unknown. Download the CSV.
Example
- You enter
- Two names,
northwindandglobexlabs, in.com,.ioand.ai. - You get
- A grid of six cells: each pairing reads Likely available (no registry record and no nameservers), Registered (with the registrar and expiry when the registry shows them) or Unknown (the registry has no RDAP service or didn't answer). Download the CSV.
- Limits
- Up to 100 a run without an account and 500 when signed in with Google, counted over a minute. Counted in pairings; 20 a request, at most 120 lookups a minute to one registry server.
How is each name checked?
Every name is joined to every extension you picked, and each domain is looked up at the registry that runs the extension. The registry's address comes from IANA's RDAP bootstrap file, so the answer comes from the registry itself, never a reseller's search box. The tool also asks DNS whether the name has nameservers.
Likely available needs two signals: the registry has no record and the name has no nameservers. Registered means the registry has a record or the name is delegated in DNS. Unknown means we couldn't tell: the registry publishes no RDAP service, didn't answer, or is limiting lookups. Unknown is never shown as available.
Why "likely" available and not available?
A registry can hold back names that have no public record: premium names with a higher price, reserved words and names blocked by policy. Those can read as likely available here, so the registrar's checkout has the final word on whether you can buy a name and at what price.
No lookup is sent through a registrar, and nothing is reserved or recorded against the names you type.
How many lookups does a run make, and how is the registry protected?
One RDAP request and one DNS query per pairing, five at a time. A registry that answers 429 (too many requests) gets one retry after a short wait, then the row says Unknown. On top of the run limit of 100 pairings a minute signed out and 500 signed in, the tool sends at most 120 requests a minute to any one registry server across all users; pairings over that come back Unknown with a note to try again in a minute.
For one name across 52 extensions, the domain extension checker is quicker. For words that end in their extension, like dele.te, try the domain hack generator.
Which extensions should a cold email domain use?
Mailbox providers judge a sending domain on its own history, not its extension, but some cheap extensions are used so heavily for spam that filters treat new names in them with suspicion. A .com, or the extension of your main domain, is the safest choice. See the best TLDs for cold email domains.
How is this different from the other domain checkers?
| Bulk domain extension checker | Domain extension checker | Bulk domain availability checker | |
|---|---|---|---|
| Input | Many names | One name | Full domains |
| Extensions | Up to 10 you pick | Up to 52 in five groups | Whatever each domain has |
| Result | A names x extensions grid | One list for the name | One row per domain |
| Best for | A naming shortlist | One favourite name | A list you already have |
Who uses this tool, and for what?
- Founders
- Shortlist brand names and see at once which are still free in .com, .io and .ai.
- Cold emailers
- Find spare sending domains for several brand variants in the extensions you trust.
- Agencies
- Check a client's naming shortlist across their markets' extensions and send the CSV.
- Domain investors
- Screen a list of words across the extensions you buy in, straight from the registries.
What can’t this tool tell you?
- Likely available isn't a guarantee: premium, reserved and blocked names can have no public record.
- Extensions whose registry publishes no RDAP service show Unknown unless DNS shows the name registered.
- No prices: only the registrar's checkout shows what a name costs.
- Up to 25 names and 10 extensions; up to 100 pairings a run without an account, 500 signed in.
- At most 120 requests a minute to any one registry server across all users.
Common questions
- How do I check if several domain names are available in different extensions?
- Paste the names into a bulk domain extension checker like this one and pick the extensions. Every name is looked up in every extension at the registry and in DNS, and you get a grid with a CSV.
- Is this bulk domain extension checker free?
- Yes. Up to 100 name and extension pairings a run without an account, and up to 500 a run when you sign in with Google, with no card.
- Why does a name show Unknown?
- The extension's registry publishes no RDAP service, didn't answer, or is limiting lookups, so we can't confirm. Unknown is never shown as available; check that pairing at a registrar.
- Can a likely available name be taken?
- Yes, sometimes. Premium, reserved and blocked names can have no public record. The registrar's checkout confirms whether a name can be bought and at what price.
- Do you register or watch the names I check?
- No. The names go to the registries' public RDAP servers and DNS only. Nothing is sent to a registrar, and the names aren't stored with your account.
- Can I type my own extensions?
- Yes. Type up to 10 extensions, such as com, io, ai, co, app or co.uk. An extension that isn't in the DNS root is marked as not a real extension.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.