Bulk Whois API - Bulk Whois API is a provider of parsed WHOIS data in JSON with simple API, competitive pricing, top notch support, and more.

SimilarWeb - SimilarWeb.com is a website analysis tool that gives you analytics information for any website.

Whoisology - Connected database of whois records and whois history

Site Rank Data - View historical rank information of websites via time series charts.

WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.

Quantcast - Quantcast Corporation is a digital marketing company that provides free audience demographics measurement and delivers real-time advertising.