The following article explains What is a web crawler and how does it work along with a brief history, who uses it and top web crawlers in the world today. All information source is given in the article.
What is a web crawler?
A web crawler is a bot that goes to different websites and usually collects data from the websites. Typically it is used for indexing. So basically it is a bot that collects data from the web. The data collected can be analyzed and then further action can be taken upon it.
Other names: Web Robot, Web Spider
Who uses it?
The web crawlers are used mainly by web search engines. They are used for indexing. So Google, Yahoo and Bing are good examples of it.
Web crawlers have been popular even since 1990`s but really gained prominence after 2000 when the internet became massive and data extraction from the internet became harder. Later on however as the data became more and more it became almost impossible to get the data from the internet. Hence web crawlers came into existence.
Web crawlers are becoming increasing popular these days and infact are becoming the norm.The web crawlers are at an all-time high and are expected to increase. Infact almost 34% of the visits to a website are already in the form of web crawlers. With big names like google, amazon and alexa all crawling pages.
Source : Incapsula Report
The biggest web crawler:
Google is the biggest web crawler. Google regularly crawls websites to analyze where it should rank the website. Also it crawls the website to see if new content has been added or not.
Top 10 famous crawlers
|Bot Name||% of Sites Crawled||Bot Type|
|Baidu Spider||89%||Search Bot|
|MSN Bot/BingBot||82%||Search Bot|
|Yandex Bot||73%||Search Bot|
|Soso Spider||61%||Search Bot|
|Sogou Spider||31%||Search Bot|
|Google Plus Share||24%||Crawler|
|Facebook External Hit||24%||Crawler|
|Google Feedfetcher||22%||Feed Fetcher|
Complete list of web crawlers
A complete list of database for all crawlers unfortunately doesn’t exist till now. However a comprehensive list was made by robots text.
How it is made?
Web crawlers are programs written usually in some programming language. The language that web crawlers can be written in are many. The most prominent one that is being used right now to crawl is python. Of course web crawling is not limited to python. You can also write computer code to crawl websties in C# and java script. The web crawlers are becoming increasing sophisticated right now.
Why use web crawler?
The reason these are being used right now is mainly
Google, Amazon and Alexa are good examples of this. They crawl the website and then analyze how good the website is. These websites crawl to analyze the status of the page. This part often is for the purpose of checking the current status of website and understanding if there is any more url`s added.
How does it work?
When you search for something in Google , Google crawler does not crawl the web then. That would take a lot of time to find all the pages that contain the search keywords. Instead, Google has run millions of web crawling and scrapings beforehand. It has already got all the content, saved in a database. So that when you run your search, it can instantly displays search results.
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