How WHOIS & RDAP Work
The two protocols behind every "who owns this domain" lookup — what they return, why RDAP replaced WHOIS, and what "available" actually means.
WHOIS: the original protocol
WHOIS is a decades-old, plain-text query protocol that lets anyone ask a domain registry "who registered this name, and when?" It works, but it has real limitations: there's no standard response format (every registry formats its text differently), no built-in way to request only part of the record, and no native internationalization for non-ASCII text.
RDAP: the modern replacement
RDAP (Registration Data Access Protocol) is the IETF-standardized successor to WHOIS. It returns structured JSON instead of loosely-formatted text, supports internationalized domain names properly, and includes a standard bootstrap mechanism so a client can discover which registry to query for any given TLD. Domain Mount queries RDAP directly (falling back to a small hardcoded registry map for a few major TLDs when the bootstrap lookup itself is unreachable).
What a registration record actually contains
- Creation & expiration dates — when the domain was first registered, and when the current registration period ends.
- Registrar — the accredited company the domain was registered through (e.g., GoDaddy, Namecheap), not the person or company using the site.
- Nameservers — which DNS servers are authoritative for the domain, a strong hint at hosting provider.
- Registrant details — historically included a name/address/email, but the vast majority of registrations today show "REDACTED FOR PRIVACY" or similar, due to GDPR and similar privacy regulations that took effect industry-wide starting in 2018.
What "this domain appears to be available" means
When Domain Mount shows a domain as available, it's reporting a confirmed 404/"not found" response from a live RDAP query — meaning the registry has no active registration record for that exact name right now. It is not a prediction; it reflects the registry's own answer at the moment you searched. That said, availability can change within minutes (someone else could register it right after you check), so always confirm directly with a registrar immediately before attempting a purchase.
Why some lookups fail
A registration lookup can fail to return data for reasons that have nothing to do with the domain itself: the registry's RDAP server can be temporarily down, a network path can be blocked, or (rarely) a TLD's registry hasn't fully migrated to RDAP yet. Domain Mount surfaces this as "Unavailable" rather than guessing, and links out to a manual WHOIS lookup as a fallback.
Once you have the nameservers, see Reading DNS Records to understand what they're pointing to.