Metasearch engine

From Wikipedia, the free encyclopedia

A meta-search engine is a search engine that sends user requests to several other search engines and/or databases and returns the results from each one. Meta search enables users to enter search criteria once and access several search engines simultaneously. Since it is hard to catalogue the entire web, the idea is that by searching multiple search engines you are able to search more of the web in less time and do it with only one click. The ease of use and high probability of finding the desired page(s) make metasearch engines popular with those who are willing to weed through the lists of irrelevant 'matches'. Another use is to get at least some results when no result had been obtained with traditional search engines.

Metasearch engines create what is known as a virtual database^{[citation needed]}. They do not compile a physical database or catalogue of the web. Instead, they take a user's request, pass it to several other heterogeneous databases and then compile the results in a homogeneous manner based on a specific algorithm.

No two metasearch engines are alike^{[citation needed]}. Some search only the most popular search engines while others also search lesser-known engines, newsgroups, and other databases. They also differ in how the results are presented and the quantity of engines that are used. Some will list results according to search engine or database. Others return results according to relevance, often concealing which search engine returned which results. This benefits the user by eliminating duplicate hits and grouping the most relevant ones at the top of the list.

Search engines frequently have different ways they expect requests submitted^{[citation needed]}. For example, some search engines allow the usage of the word "AND" while others require "+" and others require only a space to combine words^{[citation needed]}. The better metasearch engines try to synthesize requests appropriately when submitting them^{[citation needed]}.

Results can vary between metasearch engines based on a large number of variables^{[citation needed]}. Still, even the most basic metasearch engine will allow more of the web to be searched at once than any one stand-alone search engine^{[citation needed]}.

Metasearch engines are sometimes used in vertical search portals, and to search the deep web^{[citation needed]}.