Take an IP and try to look for the domain/host associated with it.
Find A, AAAA, CNAME, MX, NS, TXT, SOA DNS records of a host.
Get all possible details about an SSL certificate.
Get all possible details about a domain name.
Ping a website, server or port..
Validate JSON content and make it looks good.
Get approximate IP details.
Get details of any file type, such as the mime type or last edit date.
Check whether or not a website is using the new HTTP/2 protocol or not.