Instant Domain Search vs Lean Domain Search vs Domainr
Instant Domain Search has the widest free toolset of the three, Domainr suits developers who need a status API, and Lean Domain Search pairs one keyword with common words on .com and .blog. Domain Search King, this site, checks generated names against registries before showing them.
Published by Domain Search King · Updated
This is our own product's site, so read the comparison with that in mind. Statements about another company below come from its own pages, linked in the sources list, and are its description of itself unless we say we saw it ourselves. We ran two searches on Lean Domain Search in a browser and a registry check of 40 of its names. We ran no speed test on any tool, and no accuracy test on the others.
How do the four tools compare?
| Factor | Instant Domain Search | Lean Domain Search | Domainr | Domain Search King |
|---|---|---|---|---|
| Search on Nov 1, 2026 | Search as you type, per its homepage | Keyword search box, drawn by script. Our one test search, for "coffee", reported 5,056 available domains, counting .com and .blog separately | Search box in the page HTML; results load by script, and we did not read one | Search box on the homepage |
| Extensions | 800+ stated | .com and .blog, per its FAQ | Calls itself the API for every TLD; no count on the pages we read | .com, .ai and .io on every search; .co, .net and .org with ".com only" off; /verify takes any registrable name |
| Stated data source | Site: live registry data. MCP: its own index, rebuilt daily from zone files and DNS observations | Its FAQ rates results about 95% accurate, with a second check on click | Direct registry data access, per its homepage | RDAP at the registry, WHOIS confirmation on many extensions, with the caches listed in our method |
| Cost to search | Free with no signup, per its bulk and generator pages | 100% free, per its FAQ | Page title says "fast, free"; no price shown for web search | Free with no account; about 20 homepage searches a day per IP address |
| Bulk checks | Up to 5,000 names, CSV import and export | None found | No bulk tool found; the API bills per request | No bulk upload |
| Names for sale | Search across Afternic, Sedo, Atom and others | None found | API reports aftermarket status | Search does not list them |
| Trademarks | USPTO record search | None found | None found | Heuristic risk check, with no database search |
| API or MCP | Free MCP server with five tools, no key | None found | Paid API through Fastly, with 10,000 free requests a month | MCP server with three tools, 10 free calls a day |
| How it earns | Referral fees, per its generator page; it is also an ICANN-accredited registrar | Registration links to WordPress.com | API fees and commissions | Namecheap and Spaceship affiliate links |
Which tool fits which job?
| If you need to | Start with | Why |
|---|---|---|
| Check a list of hundreds of names | Instant Domain Search | Its bulk tool takes up to 5,000 names. We have no bulk upload. |
| Browse names already for sale | Instant Domain Search | It searches marketplace listings. We don't. |
| Look up US trademarks beside the domain | Instant Domain Search | It has a USPTO search. Ours is a heuristic flag. |
| Build domain search into your own product | Domainr | It sells a status API with published per-request pricing. |
| Pair one keyword with common words on .com and .blog | Lean Domain Search | That is what it is built for, and results can be sorted and filtered by where the word sits. |
| Name a business from one sentence, seeing .com, .ai and .io together | Domain Search King | The AI mode shows names after a registry check, and a taken .com stays on the card if .ai or .io is free. |
| Give an AI agent answers based on RDAP | Domain Search King | Our MCP tools go through RDAP, with the short caches we list. Instant's MCP page says its checks come from a daily index. |
What does Instant Domain Search do better?
Its homepage lists search across 800+ extensions, an AI generator, bulk checks, a search over marketplace listings, a WHOIS lookup, value estimates and a USPTO trademark search, and its bulk and generator pages say they are free with no signup. Its MCP server needs no key and adds trademark tools. It is also an ICANN-accredited registrar, and its registrar pricing page listed .com registration at $20 a year. We cover none of the bulk, marketplace or USPTO jobs.
Its two descriptions of the checker differ. The homepage says it queries live registry data. The MCP page says those checks use its own index built from zone files and DNS observations and send no live query to a registry, which it presents as protecting your searches, and it advises confirming with the registrar before purchase. Those may describe two different systems, and we could not tell which one answers a given web search. Our checks do query the registry, so that privacy point doesn't apply to us.
What does Domainr do better?
Domainr is the choice if you are building a product. Fastly owns it, and the Fastly pricing page lists the Domain Research API with 10,000 free requests a month, then $0.001 per request for the precise status tier up to 1 million. Its homepage says the API can separate available, premium-priced and aftermarket names, and describes direct access to registry data with "no false positives." We have not tested that claim. Its about page also says it does not front-run searches, and that it logs searches anonymously and earns commission on purchases. Our site has a route for one name at a time and no paid API tier of that kind.
Is Lean Domain Search still working?
Yes. In a browser on November 1, 2026, a search for "coffee" reported 5,056 available domains, with .com and .blog links on each name. The search box is drawn by script, so a plain fetch of the homepage HTML shows no form or input field, and the site can look switched off to an automated reader. Its FAQ calls the tool 100% free and rates it about 95% accurate, meaning about 1 in 20 listed names is actually registered, with a second check when you click a name. In our 40-name check, 39 of the first 40 .com names it listed for kombucha had no record at Verisign. One keyword is a small sample.
Where does Domain Search King fall short?
Coverage in the main search is six extensions, against the 800+ Instant Domain Search states. You can check any other extension one name at a time on the verify page. There is no list upload, no marketplace search and no trademark database. The free search has a daily cap per IP address, so an office sharing one address shares the allowance. We are not a registrar: the Register buttons are affiliate links, and we earn a commission if you buy through them. Popular keywords can first appear from a cache up to about 30 hours old before the background recheck finishes.
Generated names go through an RDAP check, and .ai and .io names need a WHOIS answer before we call them free. That matters for AI naming: in the 2026-09-01 run of our AI hallucination index, 69.5% of 2,449 AI-suggested .coms were already registered. If you came here from brand-name generators, the Namelix alternative comparison covers that category.
What could we not confirm?
- Speed and accuracy. Instant Domain Search and Domainr both make claims on these, and we ran no test.
- How many extensions Domainr covers. The homepage gives no number, and the /tlds address we tried returned 404.
- Which data source answers a web search on Instant Domain Search, as described above.
- Whether Domainr offers an MCP server, or Lean Domain Search anything beyond what is listed. "None found" in the table means absent from the pages we read, which is weaker than a statement that the feature doesn't exist.
Sources read November 1, 2026
- Instant Domain Search: homepage, bulk search, generator, MCP, registrar pricing
- Lean Domain Search: homepage and one search, loaded in a browser, FAQ
- Domainr: homepage, about, Fastly pricing
Check a Name Against the Registry
Paste one domain and see what the registry holds for it right now.
Open the verify pageFAQ
Is there a free alternative to Lean Domain Search?
Lean Domain Search itself is still free and working. For names from a keyword or a description with a registry check on .com, .ai and .io, Domain Search King is another option. For wide extension coverage or bulk checks, Instant Domain Search describes free tools for both.
Is Domainr free?
Its page title says "fast, free" and it has a search box, with no price shown for web search. The Fastly Domain Research API behind it lists 10,000 free requests a month, then per-request pricing.
Does Instant Domain Search check the registry live?
Its homepage says the checker queries live registry data. Its MCP page says MCP checks come from a daily index and send no live query to a registry. It advises confirming with the registrar before purchase.
How does Domain Search King check availability?
Through RDAP at each registry, with WHOIS confirmation on extensions where a 404 can hide reserved or premium names. Some answers are cached, and the method page lists how long.