WHAT IS CRAWLER IN SEARCH ENGINE? | HOW CRAWLER WORKS?
WHAT IS CRAWLER IN SEARCH ENGINE?:- Crawler is like something which automatically accesses a website and obtains data via a software program. It helps to learn what every webpage on the internet is about so that the information can be indexed and then can be retrieved when it’s needed. Get more information about CRAWLER in search engine by reading this article.
WHAT IS CRAWLER
A web crawler also known as spider, or search engine bot downloads and indexes content from all the web pages available on the Internet. By downloading the web pages from internet, crawler then learns what every web page is about so that the information can be retrieved whenever it is needed.
By using a software program, crawler then accesses the website and learns the fundamental goal of every web page. Crawlers are operated by search engines and by applying the algorithm to the data which is collected by spiders/ crawlers, search engines can provide relevant links in response to user search queries by generating the list of web pages that show up after a user types a search into GOOGLE or BING.
Crawlers can be explained by taking an example like a librarian, whose work is to categorize all the books and puts together a card catalog so that anyone who visits the library can quickly read the card and get the book which they want.
However, unlike a library, the Internet is not composed of physical piles of books. Web crawler works at a large level and as we know there are millions of web pages available on the internet and crawler sorts the web pages according to their category.
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HOW DO WEB CRAWLERS WORK?
As Internet is constantly changing and expanding every day, it is not possible to know that how many web pages are there on internet. Crawlers works every single second to get relevant information from the web pages and following are the main points which will help you to understand how crawlers actually works.
- Web crawler starts from a seed or from a list of URLs. As they will crawl further, they will find hyperlinks to other URLs first and then they add those to the list of pages to crawl next.
- Crawler follows a certain policies that make it more selective about which web pages to crawl and how often they should crawl those web pages again.
- Crawlers of most search engines don’t crawl the entire publicly available internet and are not intended to; instead they chose to crawl first based on number of other pages that link to that page by learning the amount of visitors that particular page gets and some other factors that signify the page’s possibility of containing important information.
- The main purpose of crawler is to get a web page that is cited by a lot of other web pages and gets a lot of visitors is likely to contain authoritative and high quality information.
- Web crawlers also decide which pages to crawl based on robots.txt protocol which is also known as robots exclusion protocol.
- Before crawling crawler checks the robots.txt file hosted by the page’s web server. A robot.txt file is a text file that specifies the rules for any bots accessing the hosted website.
WHY ARE WEB CRAWLERS CALLED ‘SPIDERS’?
The technological place also known as internet has a name called WORLD WIDE WEB where the users access. From WORLD WIDE WEB the www came which is a part of most websites URLs. It is like natural to call search engine bots “spiders,” because they crawl all over the Web which is just as same as real as the spiders which crawl on spider webs.
HOW DO WEB CRAWLERS AFFECT SEO?
SEO is the practice of optimizing web pages in order to get a rank in GOOGLE search and it stands for SAERCH ENGINE OPTIMIZARION. So if the crawlers or spider bots don’t crawl a website, then it can’t be indexed, and then the web page won’t show up in search results.
So if a website owner wants to get organic traffic on the website then it is necessary to not block web crawler bots.
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METHODS OF WEB CRAWLING
- DISTRIBUTED CRAWLING
As web is growing every single day, it has become imperative to parallelize the crawling process in order to finish downloading the web pages in a specific amount of time. A single crawling process is insufficient for large scale engines as crawler need to fetch large amounts of data in a fast way.
By distributing the crawling activity via multiple processes can help build a scalable, easily configurable system, which is fault tolerant system whenever a single centralized crawler is used all the fetched data passes through a single physical link.
Thus, splitting the load decreases hardware requirements and also increases the overall download speed and reliability and then each task is performed in a fully distributed fashion, that is, no central coordinator exists.
- FOCUSED CRAWLING
Focused crawler is designed to work by only gathering documents on a specific topic which then reduces the amount of network traffic and download. The purpose of the focused crawler is to selectively seek out pages that are relevant to the specific topic.
As the topics are specified not using keywords, but using exemplary documents. Focused crawlers analyze its crawl boundary to find the links that are likely to be most relevant for the crawl. This helps to avoid irrelevant regions of the web and leads to significant savings in hardware and network resources. All of this process helps keep the crawl more up-to-date.
There are two main components of focused crawlers that are
A classifier is used to calculate the relevance of the document by focusing on the selected topic.
A distiller searches for the efficient access point that leads to a large number of relevant documents by using lesser number of links.
So this was all about CRAWLER IN SEARCH ENGINE and we have explained different types of crawling methods available in search engines and also explained how it works and how it is important.
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