How Do Search Engines Work – Web Crawlers

There are two types of search engines. The first is by robots called crawlers or spiders.  Search Engines use spiders to index websites. When you submit your website pages to a search engine by completing their required submission page, the search engine spider will index your entire site. A ‘spider’ is an 

An automated program run by the search engine system. Spider visits a website, reads the content on the actual site, the site’s Meta tags, and follows the links that the site connects. The spider returns all that information to  A central depository, where the data is indexed. It will visit each link you have on your website and index those sites. Some spiders will only index a certain number of pages on your site, so don’t create a site with 500 pages!

How Do Search Engines Work - Web Crawlers

The spider will periodically return to the sites to check for any changed information. The moderators of the search engine determine the frequency with which this happens. A spider is almost like a book containing the table of contents, the actual content and the links and references for all the websites it finds during its search, and it may index up to a million pages a day.

Example: Excite, Lycos, AltaVista and Google.

When you ask a search engine to locate information, it searches through the index it has created and not the Web. Different search engines produce rankings because not every search engine uses the same algorithm to search through the indices. 

A search engine algorithm scans for the frequency and location of keywords on a web page, but it can also detect artificial keyword stuffing or spamdexing. Then the algorithms analyze the way that pages link to others.

Pages on the Web. By checking how pages link to each other, an engine can determine what a page is about if the keywords of the linked pages are similar to the keywords on the original page.

How Do Search Engines Work - Web Crawlers