# Domain availability checker: shortlist your SaaS domain.

Check up to 10 names across five extensions with registry RDAP snapshots. See the evidence behind every status — free, no sign-up.

Page: https://saascode.ai/tools/domain-availability-checker

## How to use

1. Enter bare names to check all five extensions, or full supported domains to check specific names.
2. Choose Check domains. A batch is limited to 50 domains with at most three requests at once.
3. Read taken, likely available and unknown separately. Export the timestamped report and confirm registration with a registrar.

## Scope

RDAP is an availability signal, not a reservation. No server route or paid lookup. Fixed registry endpoints verified 2026-10-09; .io mapping is a separately verified registry exception to the IANA bootstrap.

## References

- [IANA RDAP bootstrap](https://data.iana.org/rdap/dns.json)
- [Identity Digital RDAP service](https://www.identity.digital/help-articles/whois-faq)
- [IANA .io delegation](https://www.iana.org/domains/root/db/io.html)
- [RDAP HTTP status semantics (RFC 7480)](https://www.rfc-editor.org/rfc/rfc7480.html)

## Build your SaaS

[Find the SaaS to put on that domain](https://saascode.ai/products)

## Related tools

- [SaaS SWOT analysis generator](https://saascode.ai/tools/swot-analysis-generator)
- [SaaS development cost calculator](https://saascode.ai/tools/saas-development-cost-calculator)
- [SaaS idea generator](https://saascode.ai/tools/saas-idea-generator)
- [All free tools](https://saascode.ai/tools)

## FAQ

### Where do domain queries go?

Directly from your browser to fixed registry RDAP endpoints over HTTPS. Registry operators receive domain names and may log them. There is no SaaSCode proxy. CORS was tested on 2026-10-09; if it stops working, the result is unknown, never available.

### Does likely available mean I can buy the domain?

No. It means a registry RDAP 404 was returned for that domain. This is a signal, not a reservation. A registry may reserve names or impose eligibility rules; registration and pricing must be confirmed with a registrar. No affiliate links or third-party price claims appear here.

### Which names and extensions are supported?

ASCII names with letters, digits and internal hyphens, 1–63 characters, followed by .com, .ai, .io, .dev or .app. Punycode A-labels may be entered. URLs, paths, subdomains and other TLDs are rejected. Bare names expand to all five supported extensions.

### Which registry servers are used?

Verisign for .com, Google Registry for .dev and .app, and Identity Digital for .ai and .io. The fixed map was checked against IANA bootstrap publication 2026-09-30. .io is absent from that bootstrap; its Identity Digital endpoint was separately verified with matching registrations for github.io and git.io on 2026-10-09.

### How are taken and unknown determined?

Taken requires HTTP 200 with a matching RDAP domain record. Unknown includes timeouts, CORS or network failures, rate limits, redirects, oversized responses and unexpected data. Only HTTP 404 with RDAP errorCode 404 becomes likely available, plus Verisign’s observed empty application/rdap+json 404 response for .com. DNS absence is never used as availability evidence.

### Are there limits and caching?

Up to 10 inputs and 50 domains per batch, three concurrent requests, 10-second request timeout, 256 KiB response limit and 10 seconds between batches. Successful registration or 404 snapshots are reused in memory for up to 60 seconds and show their original check time. Registries can impose additional limits.