Domain availability checks lie (here is how to do them right)

Short answer: a one-second "available" tick from a domain search can be wrong in two directions at once — rate limits hide results, and some registries report taken domains as available. And even when the tick is correct, the price you saw is probably not the price you will pay. Check availability against two independent sources, judge cost by the renewal price, and confirm you can actually pay before you fall in love with a name.

In September 2026 I batch-checked 27 candidate domain names while picking one for a tool site. The exercise surfaced six problems, two of which produced flatly wrong answers from services that looked authoritative. This is what the raw responses taught me. Prices and rate limits change — re-verify before you buy.

Pitfall 1: aggregator services rate-limit exactly when you need them most

The intuitive approach is to send a batch of candidate names at a public aggregator such as rdap.org. I tried 27 candidates at 6 concurrent requests: the first 11 succeeded, and the remaining 16 all returned HTTP 429 (Too Many Requests).

The reason is structural. An aggregator proxies your query to the registry that operates the TLD, and the registry's rate limit applies to the aggregator's shared pool, not to you personally. Every other user of the aggregator inherits your traffic and vice versa. Batch queries — the exact moment you need reliability — are the moment the shared pool is most likely to be exhausted.

The fix is to query the registries directly. Each major registry family runs its own RDAP endpoint, and they are far more tolerant of individual traffic:

After switching to direct queries, the 429s never came back.

Pitfall 2: official endpoints can report a taken domain as available

This is the one that can cost you money, and it is not intuitive.

RDAP uses HTTP 404 to mean "not registered". That is fine in principle. The problem is multi-TLD registry operators such as Identity Digital and Radix, which run dozens of suffixes between them. If you ask one of them about a domain that belongs to a suffix they do not operate, they may still return 404 — and in your code, 404 means available.

In other words: guess the operator wrong, and a domain someone already owns comes back as buyable.

The rule I now enforce on every check:

Any "available" verdict must be confirmed by a second, independent data source. If the confirmation fails, the name is marked uncertain and never reported as available.

One extra request is cheap. Buying a name that was never for sale is not.

Pitfall 3: only checking the names you thought of first is a waste of a query

Common word roots plus .com are essentially gone. In my test, twenty-plus candidates built around one popular root came back taken across .com, .net, .org, .tools, .app, .dev and .xyz.

Candidate lists need four expansion directions, not one:

1. Root × common suffixes — the obvious batch
2. Root × other suffixes — .dev, .app, .us, .cc
3. Root × modifiers — get-, try-, -box, -kit
4. Synonym roots — useful becomes handy, utility

A batch of 60–90 candidates at 4 concurrent requests takes about 30–50 seconds. Let the whole batch finish before drawing conclusions instead of stopping after the first few answers.

Pitfall 4: the renewal price is the real price

First-year pricing is marketing. Renewal pricing is cost. What I actually measured in September 2026:

A useful yardstick: Cloudflare Registrar sells at wholesale cost, so its registration price equals its renewal price. That makes it a ruler for measuring what a suffix genuinely costs per year. The cost prices I observed at the same time:

The practical takeaway: prefer suffixes where registration price equals renewal price. Under that rule, .com, .dev and .app are the steady choices. Registrars worth caution: GoDaddy (renewal ≈$23.19, WHOIS privacy another ≈$9.99) and IONOS ($1 first year, renewal ≈$79).

Pitfall 5: confirm you can pay before you hunt for the cheapest

Overseas registrars — Cloudflare, Porkbun, Namecheap — take Visa, Mastercard or PayPal. Domestic UnionPay debit cards are frequently declined. "I have a bank card" does not mean "I can pay in a foreign currency".

Two Cloudflare constraints to accept up front: you must use its nameservers, and transferring out is more friction than with most registrars.

Pitfall 6: AdSense does not accept subdomains

This one connects domain choice directly to monetisation. Per Google's own documentation, the URL you submit to AdSense must not contain a path or a subdomain. That rules out all of these:

• xxx.pages.dev
• xxx.github.io
• xxx.eu.org
• xxx.us.kg

They are all subdomains, and applications using them are rejected. Free second-level domains are fine for practice; they are not fine for an ad-funded site. If advertising revenue is part of the plan, a real domain is not an optional saving — it is the cost of admission.

The six-point checklist

1. Batch queries: go direct to registry RDAP endpoints, not aggregators, to dodge 429s.
2. No single "available" answer is trusted: confirm with a second source, or mark it uncertain.
3. Expand candidates in four directions; run the full 60–90 batch before judging.
4. Compare renewal prices, not first-year promos — watch for the +7850% trap.
5. Confirm your payment channel works before optimising on price.
6. Planning to run ads? Then a real domain is mandatory; subdomains will be rejected.

Based on live tests of 27+ candidate domains in September 2026. Prices and rate-limit behaviour change; re-verify before you buy.