You have likely asked this question more than once. The thing is, that most people get curious about many things especially those things they interact with on a regular basis, of which Google (search) is part of most of us. Most people who’ve been intrigued by the way Google is able to get them the result to what they search in a matter of seconds would likely have asked the question ‘How Does Google Search Work?’ instead of ‘How Does Google Scrape Websites?’, they both are related since answering one would lead you to talking about the other.

So we will be talking about How Google scrapes websites and how Google search works.

How Google Search Works

Here’s exactly all you need to know on how the number one most visited and used website on the internet works. Google search works in this three steps:

  • Crawling
  • Indexing
  • Serving

It isn’t as simple as it seems but the above is just the summary of how Google works, inside one of these three lies scraping. Yes, Google scrapes data from other websites too, but before we go into that, let’s explain a little of what happens first before any website that appears on the Google SERP (Search engine Result Page) shows up on your result.

The webmaster publishes their website, they notify Google saying ‘hey! I just published my site and I want you to show it to searchers when they search (any term could fit in here) keyword’, they do this by submitting their site to the Google webmaster tools and allowing the Googlebot (Google’s web crawler) access to their website pages through the robots.txt file.
Google responds by sending it’s crawler to go through the site and confirm if it really exist, what pages are available and gets the kind of content that’s available on it.
If the site meets Google’s requirements, they start showing up on the SERP.

How Does Google Scrape Websites

For Google to index your site, it needs to crawl and then scrape contents of your website. That means, after crawling your site with the help of Googlebot (the name of Google web crawler), your website content is scraped and stored in a cached form in the Google servers.

Why does Google need to store and cache your website on its servers when your site is actually online? This is for faster delivery of search results to searchers, serving results from Google’s servers obviously would be faster than serving them from your host or any other third party server.

The first step to Google scraping any website is by first sending Googlebot to crawl the website and all of its pages and related links, by so doing Google has idea what kind of data is available on the website, the next is scraping the content of the website.
At this point Google makes use of its in-house web scraper to fetch data from the said website.

In a nutshell, a webmaster first notifies Google of their website and it’s address, then Google sends Googlebot to confirm what pages exists and are available on the website, then scraping starts after which site is indexed and ready to be served on the SERP to searchers.

The above is basically how Google scrapes websites and of course how Google search works.

If you want to start building your own Googlebot, you might want to have a look at ProxyCrawl.