The deep Web is enormous in comparison to the surface Web. Today's Web
has more than 555 million registered domains. Each of those domains can
have dozens, hundreds or even thousands of sub-pages, many of which
aren't cataloged, and thus fall into the category of deep Web.
Although nobody really knows for sure, the deep Web may be 400 to 500 times bigger that the surface Web [source: BrightPlanet]. And both the surface and deep Web grow bigger and bigger every day.
To
understand why so much information is out of sight of search engines,
it helps to have a bit of background on searching technologies. You can
read all about it with How Internet Search Engines Work, but we'll give you a quick rundown here.
Search engines generally create an index of data by finding information that's stored on Web sites and other online resources. This process means using automated spiders or crawlers,
which locate domains and then follow hyperlinks to other domains, like
an arachnid following the silky tendrils of a web, in a sense creating a
sprawling map of the Web.
This index or map is your key to
finding specific data that's relevant to your needs. Each time you enter
a keyword search, results appear almost instantly thanks to that index.
Without it, the search engine would literally have to start searching
billions of pages from scratch every time someone wanted information, a
process that would be both unwieldy and exasperating.
But search
engines can't see data stored to the deep Web. There are data
incompatibilities and technical hurdles that complicate indexing
efforts. There are private Web sites that require login passwords
before you can access the contents. Crawlers can't penetrate data that
requires keyword searches on a single, specific Web site. There are
timed-access sites that no longer allow public views once a certain time
limit has passed.
All of those challenges, and a whole lot of
others, make data much harder for search engines to find and index. Keep
reading to see more about what separates the surface and deep Web.
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