What is a Web Crawler?

August 03, 2021
Web Crawler

A web crawler also defined as a web spider or web robot is an automated script that browses the World Wide Web in an efficient, and automated manner. This process is also termed Web Crawling or Spidering. Many legitimate websites in particular search engines such as Google and Microsoft Bing benefit from Spidering as a means of providing up-to-date data. Web crawlers visit websites, take a copy of the pages they visit and then index them to afford fast searches. A crawler can also be pre-own for automating maintenance tasks on a website, such as checking links or validating HTML code.

Types of Web Crawler 

Web Crawler are not circumscribing to search engine spiders. There are other types of web crawling out there such as –

Email Crawling 

Email crawling is especially advantageous in outbound lead generation as this type of crawling benefits extract email addresses. It is worth mentioning that this kind of crawling is illegal as it breaches personal privacy and cannot be pre-own without user permission.

News Crawling 

With the occurrence of the internet, news from all over the world can be spread expeditiously around the web, and extracting data from various websites can be quite awkward. Many web crawlers can confront this task. Such crawlers are adept to retrieve data from new, old, and archived news content and read RSS feeds. They extract the following information such as date of publishing, lead paragraphs, author’s name, headlines, main text, and publishing language. 

Image Crawling 

As the name entails, this type of crawling is applying to images. The internet is full of visual representations. Thus, such bots benefit people find relevant pictures in a plethora of images across the web.

Video Crawling

Sometimes it is much painless to watch a video than read a lot of content. If you arbitrate to embed YouTube, SoundCloud, Vimeo, or any other video content into your website, it can be catalog by some web crawlers.  

Social Media Crawling 

Social media crawling is quite an alluring matter as not all social media platforms acquiesce to be a crawl. You should also bear in mind that such a type of crawling can be illegal if it breaches data privacy compliance. Still, there are many social media platform providers which are accomplished with crawling. For instance, Pinterest and Twitter acquiesce to spider bots to browse their webpages if they are not user-sensitive and do not acknowledge any personal information of the webpage. Facebook, LinkedIn are rigorous regarding this matter. 

Examples of web crawler

A lot of search engines benefit from their search bots. For instance, the most common Web Crawlers examples are such as –


Amazon web crawler Alexabot is pre-own for web content recognition and backlink discovery. If you need to keep some of your information private, you can preclude Alexabot from crawling your website. 

Yahoo! Slurp Bot

Yahoo crawler Yahoo! Slurp Bot is pre-own for indexing and scraping web pages to boost personalized content for users.  


Bingbot is one of the most prominent web spiders power by Microsoft. It benefits a search engine, Bing, to create the most relevant index for its users. 


This crawler is accomplished by the dominant Chinese search engine – Baidu. Like any other bot, it travels through a variety of web pages and glances for hyperlinks to index content for the search engine.

How do web crawler work?

Crawlers scrutinize out information that is put on the World Wide Web. The internet changes daily, and web crawlers supersede certain protocols, policies, and algorithms to make choices on which pages to crawl, as well as which order to crawl them in. The crawler evaluates content and categorizes it into an index to efficiently retrieve that information for user-specific queries. Relevant information is determined by algorithms specific to the crawlers, but commonly includes factors such as accuracy, rate, and location of keywords. Although the exact mapping of how this works is peculiar to the algorithms pre-owned by proprietary bots, the process commonly follows –

  • Web crawlers give a URL 
  • Crawlers glance through a page’s content and substantially take notes on it – what it is about, whether it is advertorial or informational, what kind of keywords it avail – so that they can assort it as accurately as feasible 
  • This data is recorded and added to a giant archive, exclusive to the search engine, called an index. When a user acknowledges a query, search engine algorithms sort through the data in this index to return the most consistent results. 
  • After their targets are index, crawlers scrutinize outbound hyperlinks, then follow them to other pages, repeating the process Ad infinitum. 

Why do I want my website to get crawl?

While many determine that when you circulate a post on a website. It will automatically be advertised to everyone searching for it through Google or Bing, this is not the case. First, your web page is urgent to be index. To index a web page, it must first be a crawl. Getting a crawl is essential because it and many search engine-specific algorithms clinch whether or not your website will get index or not.


Web crawler are an essential part of an extensive search engine that is pre-own for indexing and discovering content. Many search engine companies have their bots, for instance, Googlebot is power by the corporate colossal Google. Apart from that, multiple types of crawling are bestow to cover specific demand, such as video, image, or social media crawling.

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By Andrew

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