There are three ways that a search engine can find a website to add to its database. The first and most direct method is to accept submissions from website designers and optimizers. Most search engines have a "submit your URL" section inviting submissions from Internet users.
The second and least obvious method of finding websites is to send a "spider" to follow each and every link on, off, and through a website. New URLs encountered by the spider will be added to the database. In this way, some search engines will grow very rapidly.
Thirdly, some search engines derive the information for their listings directly from other search engines.
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