Who.is是常用的一个域名信息查询网站，不但域名好记，而且功能全面、使用方便，能够查询100余种后缀的域名，可查询域名Whois历史（可查到该域名的上一个拥有者或上一个注册商）、域名Alexa排名信息、域名DNS解析记录、搜索结果等。除了域名相关信息查询，Who.is还提供了其它三个实用的站长工具，可查询有哪些域名使用了某个DNS服务器，服务器的Ping值以及服务器的Traceroute数据（可大体了解该服务器网络速度）。

WHOIS（读作“Who is”，而非缩写）是用来查询互联网中域名的IP以及所有者等信息的传输协议。早期的WHOIS查询多以命令列接口（Command Line）存在，但是现在出现了一些基于网页接口的简化线上查询工具，甚至可以一次向不同的数据库查询。网页接口的查询工具仍然依赖WHOIS协议向服务器发送查询请求，命令列接口的工具仍然被系统管理员广泛使用。

WHOIS通常使用TCP协议43埠。每个域名或IP的WHOIS信息由对应的管理机构保存，例如，以.com结尾的域名的WHOIS信息由.com域名运营商VeriSign管理，中国国家顶级域名.cn域名由CNNIC管理。

通常情况下，域名或IP的信息可以由公众自由查询获得，具体的查询方法是登陆由管理机构提供的WHOIS服务器，输入待查询的域名进行查询。

When the Internet was emerging out of the ARPANET, there was only one organization that handled all domain registrations, which was DARPA itself. The process of registration was established in RFC 920. WHOIS was standardized in the early 1980s to look up domains, people and other resources related to domain and number registrations. Because all registration was done by one organization at that time, one centralized server was used for WHOIS queries. This made looking up such information very easy.

Responsibility of domain registration remained with DARPA as the ARPANET became the Internet during the 1980s. UUNet began offering domain registration service; however they simply handled the paperwork which they forwarded to the DARPA Network Information Center (NIC). Then the National Science Foundation directed that management of Internet domain registration would be handled by commercial, third-party entities. InterNIC was formed in 1993 under contract with the NSF, consisting of Network Solutions, Inc., General Atomics and AT&T. The General Atomics contract was canceled after several years due to performance issues.

20th century WHOIS servers were highly permissive and would allow wild-card searches. A WHOIS query of a person's last name would yield all individuals with that name. A query with a given keyword returned all registered domains containing that keyword. A query for a given administrative contact returned all domains the administrator was associated with. Since the advent of the commercialized Internet, multiple registrars and unethical spammers, such permissive searching is no longer available.

On December 1, 1999, management of the top-level domains (TLDs) com, net, and org was assigned to ICANN. At the time, these TLDs were converted to a thin WHOIS model[citation needed]. Existing WHOIS clients stopped working at that time. A month later, it[clarification needed] had self-detecting Common Gateway Interface support so that the same program could operate a web-based WHOIS lookup, and an external TLD table to support multiple WHOIS servers based on the TLD of the request. This eventually became the model of the modern WHOIS client.

By 2005, there were many more generic top-level domains than there had been in the early 1980s. There are also many more country-code top-level domains. This has led to a complex network of domain name registrars and registrar associations, especially as the management of Internet infrastructure has become more internationalized. As such, performing a WHOIS query on a domain requires knowing the correct, authoritative WHOIS server to use. Tools to do WHOIS proxy searches have become common.

In 2004, an IETF committee was formed to create a new standard for looking up information on domain names and network numbers. The current working name for this proposed new standard is Cross Registry Information Service Protocol (CRISP).

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