Generally, Google and other search engines find new pages to add to their indices by following links from one web page to another.

Some search engines, including Bing and Google, also allow webmasters to submit URLs directly, meaning that your site may get indexed even if there are no links pointing to it from the “outside world”. (Links like these are called “inbound links” in the trade.)

But we wanted to know: can Google ever find and index pages that have no inbound links, and that are never sent directly to Google via its site submission form?

We set up an experiment to find out.

In fact, the page you are reading right now is part of that experiment.

We wanted to test the following scenarios:

  1. A page with no inbound links, but whose URL is to be found in plain text (ie. not clickable). Here is an example:
  2. A page with exactly one inbound link, but which has the rel=”nofollow” attribute added. In theory, such links are not followed by web crawlers, neither is any PageRank equity transferred. But in practice? Let’s see. Here is our case-study page:
  3. A page, again, with exactly one inbound link, but with “noindex” on the destination page. This tells Google to not index the page (or, to not add it to its search results). Again, let’s see. Here is our case-study page:
  4. A page with no conventional inbound links, but which can be accessed by clicking what you might call a JavaScript pseudo-link, like this: <a href=”javascript:document.location=’'”>a javascript pseudo-link</a>. Here it is in action: a javascript pseudo-link
  5. Identical to number 4, but with the pseudo-link attached to something other than an html <a> tag. Here it is in action, using a <span> tag: a clickable javascript pseudo-link
  6. A page with no inbound links in pure html, but with an inbound link that is javascript generated, rather like .
  7. Finally, we wanted to test whether Google follows links from PDFs. So here is the PDF, which contains exactly one link to a page with no other inbound links.

Check back here in a couple of weeks to see the results of these experiments.