WhoAPI helps in quickly finding the domain names. It is also used to parse data from active domains such as Alexa ranking, name servers, date of registration and expiration, etc. It covers millions of domains registered worldwide and is extremely affordable. Review collected by and hosted on G2.com.

Its user interface is not much impressive. Also, WhoAPI provides the documentation for the errors that occurred, even though it is a good thing the documentation is heavy-handed. Review collected by and hosted on G2.com.