Glossary keyword - Crawling

Web crawler is a search engine bot that browses the World Wide Web (WWW) in an automated manner. They are also called web spiders, automatic indexers, and sometimes as web robots. The process is referred to as web crawling or spidering. Web indexing process is about web spidering because automated indexer bots crawl through one page at a time and continue till all pages have been indexed. They have the authority to check/validate the links, information, HTML, and more related aspects of the websites. 

Why is it needed?

To provide up to date data to users, most search engines use web crawling techniques. To provide fast searches for users, the spidering process helps bots while indexing downloaded pages. They also check links and validate websites’ HTML pages. Web spidering is one of the ways to identify spam messages from the world wide web and subsequently report them. 

Web crawling used for:

• Data mining, a web spider, can collect available data such as emails or postal addresses of various companies
• Crawlers can search for information hubs with specific data. For example, for news sites.
• They can be used for web analysis and collect data concerning outbound/inbound links, page views, and so on.
• Price comparisons can be maintained through the web spidering process, as well. They can track particular products on the web, and compare different prices, make a conclusion. 

Examples for Web Crawlers

• Alexa
• Yandex Bot
• DuckBuck Bot
• Sogou Spider
• Slurp Bot

How Do Crawlers work?

Crawling bots’ working scheme is about collecting information, just like the URL of websites, tag information, Meta links, and web page contents. After the collection process, bots still keep track of those URLs because they do not want to download the same page again. There are some policies such as selection policy, politeness policy, re-visits policy, and parallelization policy that helps web crawlers to determine their behavior. 

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