In order to be useful, a system like WOT needs an extensive database of website reputations. It’s crucial that we know as much of the web as possible. Thanks to our trusted sources and early testers, we already have reputations for more than 10 million websites in our database. However, domain names being hierarchical, calculating the total number of known sites is not that simple.
As the technically-oriented of you already know, the Domain Name System (DNS) forms a tree. Once you purchase a right to single node of the tree, known as a domain name, you control the entire subtree below your reserved name. For example, Google owns the domain name google.com and therefore, controls all its subdomains. This means that the reputation of a node should propagate down the DNS tree. If you trust google.com, you probably at least somewhat trust earth.google.com too.
However, there are some sites that give control of their subdomains to other people, a prominent example being blogging sites, such as LiveJournal. They choose not to oversee what content their subdomains contain, well, as long as it’s not blatantly illegal anyway. This means that livejournal.com might have several subdomains with untrustworthy content that are controlled by someone else. If we think about it, this makes livejournal.com seem less trustworthy. In our minds, the reputation of a subdomain also affects the reputation of the parent domain, and thereby, the reputations of all other subdomains. Hosting your blog in a bad neighbourhood is bad for your reputation.
Taking the hierarchical nature of domain names into account, WOT can estimate the reputation of a previously unknown site based on its position in the DNS tree. If you create a new blog hosted on, say, blogspot.com, we won’t have any data of its trustworthiness yet. Theregore, we show you a reputation estimate for your blog based on its surroundings. We sort of know what to expect. Should you prove us wrong for better or worse, our users will of course correct your reputation.
So when people ask us how many sites WOT knows, this is why it’s hard to say an exact number.