How does a search engine work?

Search engines have spiders (also called robots or crawlers) that automatically cruise the Web and collect information such as text and titles. It also collects meta-tags, the words that a web author uses to describe his or her page. These little automated cuties put it all together in a database that is indexed. When we search, our keywords are matched against only this database...not the entire web. This is why we get different results from different webpages. Another reason we get varied results is the spiders get different "marching orders" depending on the search engine's algorithms. Each search engine crawls the web differently and sometimes with a different purpose. For more information, see Search Engine Watch's How Search Engines Work.

Not convinced at how different search results can be? Take the Blind Search Test.

How do I know which search engine to use?

One way is to choose by purpose. There are lots of specialized search engines; some focus on certain genres of information (such as images, blogs, or podcasts) while others might focus on content. Check out the following links for lists of specialized databases:

Is the Internet for sale?

Read the following article from the Huffington Post and discuss the title's question with a partner: "Is it Unethical for BP to Buy Google Ads on Oil Spill-Related Keywords?"

To see how buying keywords was used in our last presidential election, check out Wired's article, Our Brand is Crisis: Prez Candidates Buy Words to Brand Each Other Online.

What about the rest of my search results?

The rest of your search results are determined by various factors such as parts of the URL, title of Web site, the meta-tags, number of links, and other factors...much like the a "secret search engine sauce". Add in the variation among search engine indexes, and you don't have necessarily have a recipe for quality information. Want to know more? Check out Search Engine Watch: How Search Engines Rank Web Pages.

Let's go global!

Search engines even vary by country or region. Those little spiders create their indexed databases using different algorithms depending upon where you live. Also, keywords might be purchased worldwide or just in certain regions. For example, look at the different placement of Amnesty International in the results list for the search Bejing Olympics.

Now you try it: Go to google vs. and type in your own search term. Is it significant that Google is localized instead of global?

Comparative Web Tools

Consider using these tools to teach web literacy within your content area. Math classes can chart results and make hypothesis about the priorities of a search engine. All content area students can search for classroom-related concepts and compare/analyze the results from...

Search engines