Then, of course, these things get cited, and linked to, and re-published, which makes them even easier to find. The books less looked at, the sites less often linked to? Not so visible. Or, as digitizedmedievalmanuscripts.org puts it:
That, of course, is not only true for manuscripts, but DMMapp collects digitised medieval manuscript libraries. There's a long list of libraries that have manuscripts digitised and online, for free - so if you are looking for some things less often looked at... look no further. (Or do, and make sure to tell them about the library if it's not yet in the list.)
Finding digitized medieval manuscripts is not an easy task: the most prominent libraries are easily found and pinpointed on the maps. Problems arise for all the other digitized libraries that are not discoverable through search engines for many reasons (the website is not optimized or not accessible by crawlers and doesn't appear on web searches, the library is in a language different from English only, or, more in general, the website is difficult to access due to poor web design).