given a URL, how do I find the domain registrar and the web host?

Question

If I had a domain name, and wanted to find the registrar and the hosting company for that domain, how do I do that? Is there any central registry that keeps track of it? If yes, is there any API to query that database?

Same way, how to find out the web host?

Answer 1

You can find the domain registrar by querying the WHOIS database(s). There are actually multiple databases, depending on the Top Level Domain (TLD). For example, .com and .net are handled by Verisign. There are a handful of RFCs that describe how to query this information, along with a number of available tools that can act as a front-end for you.

For example, if you have access to a Unix or Linux command line, you can use the whois command:

$ whois example.com

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

   Domain Name: EXAMPLE.COM
   Registrar: RESERVED-INTERNET ASSIGNED NUMBERS AUTHORITY
   Whois Server: whois.iana.org
   Referral URL: http://res-dom.iana.org
   Name Server: A.IANA-SERVERS.NET
   Name Server: B.IANA-SERVERS.NET
   Status: clientDeleteProhibited
   Status: clientTransferProhibited
   Status: clientUpdateProhibited
   Updated Date: 26-mar-2004
   Creation Date: 14-aug-1995
   Expiration Date: 13-aug-2011

Last update of whois database: Mon, 01 Nov 2010 16:21:30 UTC

[. . .]

The Registry database contains ONLY .COM, .NET, .EDU domains and
Registrars.
% IANA WHOIS server
% for more information on IANA, visit http://www.iana.org
% This query returned 1 object

domain:       EXAMPLE.COM

organisation: Internet Assigned Numbers Authority

created:      1992-01-01
source:       IANA

If you don't have access to a Unix/Linux command line, you can use a large number of online web interfaces to the WHOIS database. Googling for 'whois' will turn up numerous options.

Finding the webhost for a website is significantly more difficult. You can find out who owns the IP address space using the same whois command as above, and querying the appropriate IP database. For example, to look up 192.168.1.1, I might do:

$ whois 192.168.1.1
#
# Query terms are ambiguous.  The query is assumed to be:
#     "n 192.168.1.1"
#
# Use "?" to get help.
#

#
# The following results may also be obtained via:
# http://whois.arin.net/rest/nets;q=192.168.1.1?showDetails=true&showARIN=false
#

NetRange:       192.168.0.0 - 192.168.255.255
CIDR:           192.168.0.0/16
OriginAS:
NetName:        PRIVATE-ADDRESS-CBLK-RFC1918-IANA-RESERVED
NetHandle:      NET-192-168-0-0-1
Parent:         NET-192-0-0-0-0
NetType:        IANA Special Use
NameServer:     BLACKHOLE-1.IANA.ORG
NameServer:     BLACKHOLE-2.IANA.ORG
Comment:        This block is used as private address space.
Comment:        Addresses from this block can be used by
Comment:        anyone without any need to coordinate with
Comment:        IANA or an Internet registry. Addresses from
Comment:        this block are used in multiple, separately
Comment:        operated networks.
Comment:        This block was assigned by the IETF in the
Comment:        Best Current Practice document, RFC 1918
Comment:        which can be found at:
Comment:        http://www.rfc-editor.org/rfc/rfc1918.txt
RegDate:        1994-03-15
Updated:        2010-03-15
Ref:            http://whois.arin.net/rest/net/NET-192-168-0-0-1

OrgName:        Internet Assigned Numbers Authority
OrgId:          IANA
Address:        4676 Admiralty Way, Suite 330
City:           Marina del Rey
StateProv:      CA
PostalCode:     90292-6695
Country:        US
RegDate:
Updated:        2004-02-24
Ref:            http://whois.arin.net/rest/org/IANA

OrgTechHandle: IANA-IP-ARIN
OrgTechName:   Internet Corporation for Assigned Names and Number
OrgTechPhone:  +1-310-301-5820
OrgTechEmail:  abuse@iana.org
OrgTechRef:    http://whois.arin.net/rest/poc/IANA-IP-ARIN

OrgAbuseHandle: IANA-IP-ARIN
OrgAbuseName:   Internet Corporation for Assigned Names and Number
OrgAbusePhone:  +1-310-301-5820
OrgAbuseEmail:  abuse@iana.org
OrgAbuseRef:    http://whois.arin.net/rest/poc/IANA-IP-ARIN

#
# ARIN WHOIS data and services are subject to the Terms of Use
# available at: https://www.arin.net/whois_tou.html
#

However, that just tells you who owns the IP address space, and is not a guarantee of anything else. That address space might belong to a company that hosts their own web server, or it might belong to a hosting company that hosts a website for someone else (or multiple websites on that IP, for multiple customers). Additionally, the IP address space might be owned by an ISP, and leased/used by a company. Many, many options, and very little certainty, for this.

Answer 2

The easiest way to find the registrar would be going to the following website. http://whois.domaintools.com/

To find the host usually means running a traceroute to the IP address of the website from command line or linux/mac shell such as.

tracert www.websitename.com or traceroute www.website.com

this is not always 100% since the web host may not be the same host as the database and in addition not always guarantee of hitting the target in the event its reaching a CDN.

these should help get you started however, best of luck.