Search Engine Optimization Basics: How Search Engines Work

To succeed in search engine optimization, you have to understand how search engines work.

A search engine is an information retrieval system which is designed to find information stored on any kind of computer system, whether it be an office network or the World Wide Web.

A search engine allows the user to ask for desired information by specifying a word or phrase and retrieves a list of all items in its database that contain the specific word or phrase. Usually, the results list is arranged with respect to relevancy to the original search. Search engines regularly update their databases and retrieve desired information quickly and efficiently.

Without any further qualification, the term search engine usually refers to an internet search engine. These search engines store information about large numbers of web pages which they retrieve from the internet themselves.

An automated web crawler or spider is used to follow every link it sees and then analyze the contents of each webpage. The spider then determines how the page should be listed in its database for future retrieval.

When a user is researching a topic on the Web, he enters keywords into the search engine, the search engine looks them up in its database and then provides the user with a list of best-matching web pages, according to the criteria it uses to determine relevancy.

Google and most other search engines take into account over 150 factors to determine relevancy. One of these factors is PageRank, an algorithm based on citation analysis developed in the 1950’s by Eugene Garfield at the University of Pennsylvania. PageRank “remembers” where it has been and uses the number of cross-links between pages to create virtual communities of web pages.

Search engine results pages (SERPs) usually contain a short summary of each page found, including its title and parts of the text. Most search engines today allow Boolean Searches, in which the terms AND, OR and NOT are used to further narrow down a topic.

Another advanced feature available on most search engines is proximity search, which allows the user to specify the distance between the keywords that the user has listed.

Search engines face many challenges in today’s ever-changing society. The Web is growing too fast for search engines based on today’s technology to be able to keep up with it. Web pages are frequently changing or updating their content which forces search engines to revisit them.

Searching via keywords can result in false positives, as these words can show up in documents totally unrelated to the desired topic. Sometimes a search engine just cannot find what the user is looking for based on relevancy.

Some search engines rank based not on relevancy but on the amount of money they are paid by the website owner. Website owners can take advantage of the search engines and manipulate them into displaying their pages in higher results.

Secure pages pose another problem. Search engines cannot browse them for technical reasons or will not list them for privacy reasons.

Most search engines make their money from advertising revenue and some, in order to increase revenue, will allow advertisers to pay to have their site ranked higher in search results.

These search engines often do not make it clear to the user that this has happened. The more ethical search engines display advertisements or sponsored results in an area that is obviously separate from that of the algorithmically determined results.

Every time a user clicks on one of these ads or sponsored results the search engine makes money. The majority of search engines are run by private companies that use their own specific algorithms to return results from closed databases.

Most Popular Search Engines

According to, the most widely used search engines are as follows:

  1. Google
  2. Yahoo! Search
  3. MSN Search
  4. AltaVista
  5. AOL NetFind
  6. Ask
  7. Fast
  8. Gigablast
  9. Netscape Search
  11. Wisenut
  12. Industrial Search Engines

The first three are considered to be the first-tier search engines. The remaining engines are an alphabetical listing of what are considered to be second-tier search engines.


Comments are closed.