WEB CRAWLER: Your Neighborhood Aunt

Today the world is at your fingertips. This is a fact, as the web is full of information. Facing a problem? willing to buy something? Or anything else, the first thing u search is the net, but where to look for when there are trillions of pages on the web? And here comes Search Engine to your rescue, but how does search engine know where to look for and recommend the exact plan? Your answer is with the “Web Crawler”.

Web Crawlers are computer programs that search the web. In simple terms they read whatever they find on the pages. The web crawler scans the web pages to see the positioning and uses of the words and this process is termed as “INDEXING”. Web crawler/bots or the automatic indexer (are the same) scan the web regularly to follow a proper indexing and ensure enhanced user experience and also helps in website optimization.

Eg: if you are selling a laptop, it is important to write about it on the website. If this is not done search engine will never show your website, when people search for the product.

Once a web crawler is given a list of URLs (also called seeds) to inspect, it goes around visiting each website and downloading the content. It also spots out all the hyperlinks present on the website and adds them to the list of URLs to visit (also termed as the crawl frontier). It is almost a very exhausting work, as there are numerous website existing and many more are created on a daily basis.

The web crawler is just like your “Neighborhood Aunt” who wants to know everything happening in your life and eagerly waits for new updates, likewise, the crawler keeps searching for the new content in your website in order to keep a database which can be shared when the need arises. The web crawler also knows that the meta tag, the heading with keywords and the first few sentences are likely to be important in context of a page.  The web crawler trawls the web on a daily basis to ensure that their date is maintained up-to-date and therefore as a website owner it is important for you to have fresh contents on the website, otherwise the crawler might think it to be a dead one, and wouldn’t show the desired result also web crawlers plays an important role in ranking up your website.

Crawlers feeds on information by visiting systems and often visit sites without consent. Issues of schedule, load, and "politeness" come into existence when huge collections of pages are retrieved. There are mechanisms for public sites, who doesn’t wish to be crawled.

We can control the activities of the crawler by creating a robot.txt file and writing the desired instructions like if we want the crawler to index some part and to ignore the rest, we can simply write it in the file.