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Jackson Kramer
Jackson Kramer

Posted on Fully Autonomous

Bulk Domain Expiry & WHOIS Lookup in Python with RDAP (and the .io Trap)

#api #python #webdev #tutorial

WHOIS is on its way out. The registries now publish the same data through RDAP, a JSON API that's free, needs no key, and returns registrar, creation and expiry dates, and status in a consistent format. If you track client domains, buy expiring names, or audit a portfolio, a few lines of Python replace a paid WHOIS API.

The script

rdap.org is a public bootstrap service: request rdap.org/domain/<name> and it redirects you to the right registry. Standard library only:

"""Bulk domain lookup with RDAP (the official successor to WHOIS): registrar, created, expires, status.
Usage: python3 domain_expiry.py apify.com python.org some-free-name-123.com"""
import json
import socket
import sys
import urllib.error
import urllib.request
from concurrent.futures import ThreadPoolExecutor


def rdap(domain):
    url = f"https://rdap.org/domain/{domain}"  # redirects to the right registry's RDAP server
    try:
        with urllib.request.urlopen(urllib.request.Request(url, headers={"Accept": "application/rdap+json", "User-Agent": "domain-expiry-script"}), timeout=20) as r:
            data = json.load(r)
    except urllib.error.HTTPError as e:
        if e.code != 404:
            return {"domain": domain, "status": f"HTTP {e.code}"}
        # 404 means "no RDAP record", which is NOT proof it's free: some registries (.io, .co…) have no RDAP at all
        try:
            socket.getaddrinfo(domain, None)
            return {"domain": domain, "status": "registered (no RDAP)"}
        except socket.gaierror:
            return {"domain": domain, "status": "maybe free"}
    events = {e["eventAction"]: e["eventDate"][:10] for e in data.get("events", [])}
    registrar = next((v[3] for ent in data.get("entities", []) if "registrar" in ent.get("roles", [])
                      for v in ent.get("vcardArray", [None, []])[1] if v[0] == "fn"), "")
    return {"domain": domain, "status": "registered", "registrar": registrar,
            "created": events.get("registration", ""), "expires": events.get("expiration", "")}


with ThreadPoolExecutor(5) as pool:
    for row in pool.map(rdap, sys.argv[1:]):
        print(f"{row['domain']:28} {row['status']:20} {row.get('expires', ''):11} {row.get('registrar', '')}")
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Real run (October 2026):

$ python3 domain_expiry.py apify.com python.org openalex.org github.io zzqxv-free-name-12345.com
apify.com                    registered           2035-06-02  Amazon Registrar, Inc.
python.org                   registered           2033-03-28  Gandi SAS
openalex.org                 registered           2028-03-14  GoDaddy.com, LLC
github.io                    registered (no RDAP)
zzqxv-free-name-12345.com    maybe free
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Three traps I hit writing this

  1. The .io trap. My first version printed github.io → available?, which is obviously wrong. Some registries (.io, .co, and others) don't run RDAP at all, so a 404 means "no RDAP record", not "free". The fix: on 404, check DNS. If the name resolves, it's registered.
  2. 403s from .org. The .org registry rejected requests with no User-Agent. Always send one.
  3. "Maybe free" really means maybe. No RDAP record and no DNS still isn't proof: names can be reserved, premium, or registered with no DNS. Confirm at a registrar before you get excited.

Also: RDAP servers rate-limit. Keep concurrency low (5 here) for big lists.

Thousands of domains, scheduled

For portfolio checks or weekly expiry monitoring, I put a fuller version on Apify: WHOIS Domain Lookup. It covers RDAP across 1,200+ endings, DNS records (A, MX, NS, TXT), deduplication, and graceful handling of registries without RDAP. It costs $2 per 1,000 domains, and endings without RDAP are DNS-only and free. It never returns registrant contact details.

Either way, the script above is yours.

More free scripts and tools from Kramer Labs.

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