Protocols
RDAP vs WHOIS, and why the difference is not cosmetic
WHOIS returned free text that differed at every registrar. RDAP returns structured JSON with defined status codes. For anything automated, that is the whole difference between parsing and reading.
RDAP — the Registration Data Access Protocol — is the replacement for WHOIS. It is not a new front end over the same service. It is a different protocol with a different data model, and for anyone writing software against it the difference is substantial.
The change is now mandatory
ICANN's RDAP amendments to the base gTLD Registry Agreement and the 2013 Registrar Accreditation Agreement took effect, and on 28 January 2025 the obligation to provide WHOIS over port 43 and the web sunset for gTLD registries and registrars. A narrow set of legacy exceptions remains — .com, .name and .post — but for the rest, RDAP is the required interface and WHOIS is optional.
In practice this means code that still parses WHOIS text is working against a service its provider is no longer obliged to run.
What actually differs
| WHOIS | RDAP | |
|---|---|---|
| Transport | Port 43, plain TCP | HTTPS |
| Response | Free text, no schema | JSON, defined in RFC 9083 |
| Statuses | Prose, registrar-specific wording | Fixed vocabulary, e.g. redemptionPeriod |
| Errors | Text you have to recognise | HTTP status codes |
| Finding the server | Hard-coded lists | IANA bootstrap registry |
| Internationalisation | Inconsistent | Specified |
Structured status is the important one
Under WHOIS, establishing that a domain was in redemption meant matching strings against output that differed between registrars, changed without notice, and was sometimes translated. Every WHOIS parser accumulated a pile of regexes, and every one of them broke silently — returning "not in redemption" for a domain that was, because the wording had shifted.
RDAP returns a status array drawn from a fixed vocabulary. redemptionPeriod is either present or it is not. There is nothing to interpret, which means there is nothing to misinterpret.
Bootstrap replaces hard-coded server lists
WHOIS gave no standard way to discover which server was authoritative for a TLD, so tools shipped static maps that went stale. RDAP publishes the IANA bootstrap registry: a machine-readable mapping from TLD to RDAP base URL. A new TLD becomes queryable without a code change.
Errors stop being ambiguous
A WHOIS query for a non-existent domain and a WHOIS query that was rate-limited could both return prose. Distinguishing "this name is free" from "the server declined to answer" was guesswork, and getting it backwards means reporting a registered domain as available. RDAP answers 404 and 429, which cannot be confused.
RDAP does not mean more personal data. Registration contact details are still redacted under GDPR and ICANN policy in most cases. What RDAP improves is the structure and reliability of the record, not its visibility.
What did not get better
RDAP is a protocol, not a guarantee of data quality. Registries still differ in what they publish: some omit expiry dates entirely, some publish events the others do not, and ccTLDs are under no ICANN obligation at all. Treating an expiry date as optional rather than assumed is still necessary — it is simply now a missing field rather than a parsing failure.
Common questions
Is WHOIS dead?
For gTLDs, largely. Since 28 January 2025 registries and registrars are no longer required to provide WHOIS over port 43 or the web, with narrow exceptions for .com, .name and .post. Many still run it voluntarily, but it is no longer the contractual interface.
What RFC defines RDAP responses?
RFC 9083 defines the JSON response format, and RFC 9082 defines the query format. Both replaced the earlier RFC 7482 and 7483.
How do you find the right RDAP server for a TLD?
The IANA bootstrap registry at data.iana.org/rdap/dns.json maps each TLD to its RDAP base URL. It is fetched rather than hard-coded, so new TLDs work without a code change.
Does RDAP expose registrant contact details?
Usually not. Redaction under GDPR and ICANN policy applies to RDAP just as it did to WHOIS. RDAP improves the structure and reliability of the record, not how much personal data it contains.
Built on RDAP from the first line
DropPerch queries the authoritative registry over RDAP for every domain you watch, across more than 1,500 TLDs in the IANA bootstrap registry.