RDAP vs WHOIS
RDAP returns structured JSON over HTTPS with a defined schema. WHOIS returned free text over port 43 in whatever shape each registry chose.
RDAP returns structured JSON over HTTPS with a defined schema. WHOIS returned free text over port 43 in whatever shape each registry chose. Both answer the same question about a domain.
| WHOIS | RDAP | |
|---|---|---|
| Transport | TCP port 43, plain text | HTTPS |
| Response | free text, no schema | JSON, defined by RFC 9083 |
| Finding the server | a list you maintain | IANA bootstrap registry |
| Internationalization | ASCII in practice | UTF-8 throughout |
| Access control | none | standard HTTP authentication, so registries can tier access |
| Status of a name | a text line | structured status codes |
| Required for gTLDs | not since 2025-01-28 | yes |
What actually changes for a script
The parse disappears. Instead of matching "Creation Date:" against a dozen registry formats, a client reads the events array and takes the entry whose eventAction is registration.
Errors become HTTP status codes. A name that does not exist is a 404 rather than a sentence, and a rate limit is a 429 rather than silence. That alone removes a category of bug where a throttled response was parsed as an empty record and cached as "no registration data".
What Domduck records
RDAP only, once per domain. See RDAP for the fields.
Why it matters
The migration is mostly finished for generic top-level domains and mostly not finished for country ones, so any tool touching both has to handle two worlds for years. The honest position for a domain tool is to say which it used, per reading, rather than to present one merged answer.
If you are moving a script: keep the domain input the same, replace the port 43 call with an HTTPS GET, resolve the base URL through bootstrap, and read fields by name. The rest of the work is deleting your parser.
Related
- RDAPRDAP is the Registration Data Access Protocol: a JSON web API that returns who registered a domain and when, replacing WHOIS.
- WHOISWHOIS is the 1980s text protocol on port 43 that returned domain registration details, now replaced by RDAP for generic top-level domains.
- RDAP bootstrapRDAP bootstrap is how a client finds the right server for a domain: fetch IANA’s registry, match the top-level domain, get the base URL.
Primary source: RFC 9083, the RDAP JSON responses