How Search Engines Work


How to Search the Web

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What Is the Internet?

Understanding what the Internet is and how it works can enhance your online ... read more »

Web Site Credibility

Finding information on the Web is like being a police detective: Your information is only as good ... read more »

How Search Engines Work

Search engines are online software programs designed to help users locate relevant Web sites, and are some of the most highly trafficked sites out there. Understanding how search engines work can help you get the results you want and sort through the irrelevant, misleading results you’ll undoubtedly encounter.

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  • When you enter a keyword (that is, a significant term or phrase related to the Web site you hope to find) into a search engine, you're not searching the entirety of the Web. Rather, you're searching the list of Web sites that the search engine has indexed (which can be in the billions). If the search engine hasn't added a Web site to its index, it cannot include it in the search results.
  • Search engines sift through text on Web pages using computer programs called spiders. "Spiders" crawl on the "Web," get it?
  • Spiders are very fast but they can travel only through the hyperlinks that connect Web sites. If a page isn't linked to any other pages, spiders can't find it. The part of the World Wide Web that is not linked is called the "invisible Web" or the "deep Web." It may contain information highly relevant to your search. To find resources on the invisible Web, see "The Invisible Web" and "Web Directories" sections of this guide.
  • Search engines don't know why you want information—they simply find information according to the words you've entered. These results are not recommendations; search engines don't rank their results by the content of each site. They use mathematical equations (or algorithms) to rank them, and the formula may have little to do with a site's legitimacy or value to you.
  • Companies have gotten wise to the way that search engines work. This has created an environment where Web pages are created and customized with the goal of appearing near the top of a search engine’s results list regardless of their credibility or usefulness. This practice is called "search engine optimization," and it's one reason that not all of your search results will be relevant or trustworthy.
  • The "Help," "About" or "Preferences" sections of a search engine site often have helpful tips for using that particular search engine to your advantage. For example, if you’re looking for a definition, Google tells you to add “define:” to the beginning of your keyword. Thus, a search for “define: search engine” in Google will give you a list of definitions for “search engine” from around the Web. Similar tricks are innumerable, and all search engines have them. Google has a complete list of “search operators.”
  • There is more than one kind of search engine. General search engines, also called “horizontal” search engines, search for all types of information. “Vertical” search engines search only within certain topics. “Meta” search engines search other search engines. Using the kind that does exactly what you need can improve your search results.
  • If you have trouble finding the information you want, ask yourself: Is my keyword too general? Too specific? Are there useful synonyms? Could related topics be more effective?
    • Do you get so many results that you can’t find the sites that answer your question? Here’s how to reduce the number of results:

      Use more than one word in your search. For example, type "chicken salad sandwich" instead of just "sandwich."

      Try to be more specific in your terms. If you want a panini, type "panini" instead of "sandwich."

      Use "and" instead of simply typing two words (for example, "soup AND sandwich"), and your results will include only sites that contain both terms.

      Use "not" to exclude certain terms from your results: "sandwich NOT bologna."
    • Want more search results? Try using fewer words when you search. Typing "Reuben sandwich" instead of "classic Reuben sandwich" will yield more results. By using the term "or" and trying a few related words at once ("sandwich OR gyro OR panini"), you increase your results exponentially.

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