The Evolution of Web Crawlers | Web Spiders and Crawlers are Examples of Search Engine

What is Web Crawling? How it works & Examples. All search engines need to have crawlers, some examples are:

Written by Niel Patel · 4 min read >
web spiders and crawlers are examples of

Even though many internet users are still puzzled by the web crawlers, they’ve been around for quite some time and have quite an exciting and long history. The very first version of a web crawler was designed to gather various statistics about the internet. 

Web spiders and crawlers are examples of Search Engine

Then the creators of web crawlers decided to extend their functions from simple data gathering to web page and app indexing for search engines.

The Evolution of Web Crawlers

Today, modern, advanced web spiders are designed to use the power of automation to perform an array of different functions, from filtering information and removing outdated web pages to performing vulnerability and accessibility checks on web pages and applications. 

The ongoing expansion of the internet and its immense complexity developed quite a few problems when crawling the web. Let’s see how crawling evolved into what it is today and name some of the improvements made so far.

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What is a web crawler: detailed overview

The process of web crawling refers to using the power of automation to browse web pages and applications to find the most relevant information contained on the web. But what is a web crawler exactly? 

A web crawler is a software program that crawls the web by simulating the internet users’ behavior to browse the web pages and download the most relevant data. Since internet users generate incredible amounts of data daily, finding relevant data is virtually impossible without search engines. Here is a more detailed definition of what is a web crawler.

However, search engines can’t learn about the latest data without the help of web crawlers. These little bots constantly crawl the web in search of the latest updates to provide search engines with the latest, up-to-date information for the search engine database. 

Web crawlers play a vital role in the online world, and the internet couldn’t function without them. They perform several critical roles, including:

  • Context indexing for search engines;
  • Performing automated model checking and testing of web applications;
  • Automated testing for vulnerability and security assessment.

Now, let’s delve deeper into the history of web crawlers to better understand their evolution.

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History of webcrawler search engine

The very first web crawlers saw the light of day in 1993. There were four predecessors to modern-day web crawlers:

  • RBSE spider
  • WWW Worm
  • Jump Station
  • WWW Wanderer

These four web spiders were in charge of gathering statistics and information about the web using a collection of seed URLs. These web crawling bots iteratively download URLs to gather the most relevant links and update their local repository of downloaded web pages.

MOMspider and WebCrawler

In 1994, the web crawler family welcomed two new bots: MOMspider and WebCrawler. These two spiders did all the things their older brothers could do with one difference – they were more intuitive and could understand the concepts of blacklisting and politeness. 

The biggest improvement these new crawlers brought to the table was the ability to download multiple web pages simultaneously and effectively index millions of links.

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Google – crawler based search engine

In 1998, the largest web crawler was introduced, and its name was Google. This crawler was designed to address the ever-increasing challenge of scalability. 

Google effectively handled this challenge in several ways:

  • It used techniques such as indexing and compression to reduce disc access time by leveraging low-level optimization processes.
  • It optimized the resources available to the web crawling bots by eliminating outdated and less visited web pages using complex calculations to determine the probability of an internet user visiting particular web pages. That’s how Google introduced the concept of freshness.
  • Google developed a unique architecture, called master-slave architecture, to further address the issue of scalability. In this architecture, a master server or URLServer was in charge of dispatching relevant links to a set of slave nodes. The slave nodes download the links and retrieve the assigned pages to Google. Thanks to this, Google reached 100 link downloads per second.

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Mercator – data crawling

Mercator was a web-crawling robot introduced in 1999 with the main goal of solving the issue of web crawling extendability. Mercator used a modular Java-based framework that allowed for the integration of third-party components that helped Mercator to quickly discover the outdated web pages and remove them from the web.

WebFountain – data crawling

Introduced in 2001, WebFountain was a distributed web crawling tool that didn’t only index web pages but copied them as well. It created incremental copies of crawled pages and stored them in local repositories.

Modern crawlers

The evolution of crawlers brought many new versions of crawling bots, such as:

  • Polybot, search, and UbiCrawler(2002)
  • Li et al, Loo et al, and Exposte et al (2003-2005)
  • IRL-bot (2008)

All these crawlers contributed to solving the problem of scalability and expandability. 

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How webcrawler search engine improved

The last decade brought the most advanced technology the world has ever seen. This technology fueled the evolution of the internet, changing how internet users interact with web pages and data encryptions, platforms, and communication algorithms. 

The need for covering all forms of data qualitatively and frequently has become the primary concern. That’s how the second generation of crawler bots came to be, changing the crawlers’ data analysis abilities. Modern bots are now capable of fulfilling multiple purposes and multitasking. They can work with countless information platforms and web databases. 

The biggest game-changers in the game of web crawling are:

  • Distributed crawlers – also called multi-threaded spider bots, these crawlers use advanced cloud computing techniques to crawl millions of web pages in mere seconds.
  • Circa or Heritrix crawler – this Java-based crawler can crawl and index millions of pages and download and store any web page-related information and archive websites.
  • Crawljax – an advanced crawling bot that can crawl and index Rich Internet apps with hidden data.
  • Mobile web crawler – since mobile has the power to change internet trends, mobile crawlers are needed to tap into heavy traffic being generated by the ever-increasing number of mobile users, including mobile e-learning and mobile commerce solutions.
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What are the examples of web crawling?

All search engines need to have crawlers, some examples are:

  • Amazonbot is an Amazon web crawler for web content identification and backlink discovery.
  • Baiduspider for Baidu
  • Bingbot for Bing search engine by Microsoft
  • DuckDuckBot for DuckDuckGo
  • Exabot for French search engine Exalead
  • Googlebot for Google
  • Yahoo! Slurp for Yahoo
  • Yandex Bot for Yandex


The more the internet evolves, the greater the need for more enhanced and adaptive web crawlers that can cope with the incredible amount of web pages and data on the web. What used to be just a simple tool for fetching internet-related statistics evolved into an entire industry on its own. Today, the internet wouldn’t be able to evolve without the assistance of crawling bots.

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