A web crawler is a relatively simple automated program or script that methodically examines or “crawls” web pages to create an index of the data it is looking for; These programs are generally intended for one-time use, but can also be scheduled for long-term use. There are several uses for the program, perhaps the most popular being by search engines that use it to deliver relevant websites to Internet users. Other users include linguists and market researchers or anyone trying to find information on the Internet in an organized way. Alternative names for a web crawler include web spider, web robot, bot, crawler, and auto-indexer. Tracker programs can be purchased on the Internet or from many companies that sell computer software, and the programs can be downloaded to most computers.
Web crawlers and other similar technologies use algorithms, complex mathematical equations, that are key to producing targeted search results.
common uses
There are many uses for web crawlers, but essentially a web crawler can be used by anyone who wants to collect information on the internet. Search engines often use web crawlers to collect information about what is available on public web pages. Their main purpose is to collect data so that when Internet users enter a search term on their site, they can quickly provide the Internet user with relevant sites. Linguists can use a web crawler to perform textual analysis; that is, they can search the Internet to determine what words are commonly used today. Market researchers can use a web crawler to determine and assess trends in a given market.
Web crawlers examine web pages to create an index of data.
Web crawling is an important method of collecting data and keeping up with the rapid expansion of the Internet. A large number of web pages are continuously added every day and the information is constantly changing. A web crawler is a way for search engines and other users to regularly make sure their databases are up to date. There are various illegal uses of web crawlers as well as hacking a server to get more information than is provided for free.
How does it work
When a search engine crawler visits a web page, it “reads” the display text, hyperlinks, and the content of various tags used on the site, such as keyword-rich meta tags. Using the information collected from the crawler, a search engine will determine what the site is about and index the information. The site is then included in the search engine’s database and in their page ranking process.
Web crawlers can only operate once, for example for a single given project. If their purpose is something long-term, as is the case with search engines, web crawlers can be programmed to periodically scan the Internet to determine if there have been any significant changes. If a site is experiencing heavy traffic or technical difficulties, the spider can be programmed to notice and revisit the site, hopefully after the technical problems have subsided.
Web crawlers can be operated for only one specific project.
