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 you are looking for; these programs are usually meant to be used only once, but they can also be programmed for long-term use. There are several uses for the program, perhaps the most popular being search engines that use it to provide relevant websites to web surfers. Other users include linguists and market researchers or anyone trying to search for information on the Internet in an organized manner. Alternative names for a web crawler include web spider, web robot, bot, crawler, and auto-indexer. Crawler 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 math equations, which are key to producing targeted search results.
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 gather information about what is available on public web pages. Its main objective is to collect data so that when Internet users enter a search term on your 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 scour the Internet to determine which 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 ensure that 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 what is provided for free.
How it works
When a search engine crawler visits a web page, it “reads” the visible text, hyperlinks, and content of the various tags used on the site, such as meta tags with many keywords. 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 its page ranking process.
Web crawlers can only operate once, say, for a given single project. If your 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 this and revisit the site again, hopefully after the technical issues have subsided.
Web crawlers can be operated for a specific single project.