WhoIsHostingThis.com is a webmaster tool that lets you discover which web host any website uses.
Most webmaster tools struggle with this one simple question: who really hosts a website?
For example, NetCraft.com might give you the impression that HostGator.com is hosted by The Planet. Obviously it's not - it's hosted by HostGator! - but they rent space in The Planet's datacenter range.
Knowing the real web host is invaluable if you need to issue a DMCA complaint, libel papers or report a DDoS attack as a matter of urgency.
WhoIsHostingThis.com uses multiple data sources to provide more accurate results, as well as providing reviews of web hosting brands, hosting comparison tool and a DMCA takedown service.
The tool has been featured in the New York Times, LifeHacker and Download Squad.
It is also used by the UK government and the Association of Chief Police Officers in the UK for tracking down website hosts.