Have you ever wondered what is the mechanism by which, when you search for something on a search engine, the results page (called SERP) returns links in line with what is required, even at the cost of going fishing in the depths of the web?
What happens is easy to tell, but hard to imagine: it's a matter of fathoming the whole web in an instant in search of keywords, tags and metatags that can give you a result that satisfies you. And who will ever be the diver who will dive into the ocean depths of the internet to accomplish this feat? That's right: the web crawler.
Web Crawler: the definition
Web Crawlers have many names: spiders, robots and bots are just a few, but they describe very well what they do. In a nutshell: they explore the World Wide Web to index the Internet pages on search engines' mandates.
Search engines do not know magically what sites exist on the Net, they must first detect them and put them in their indexes so that they can present them again when a search is made.
Why are Web Crawlers essential?
To simplify the concept, let us take the example of a supermarket. Let's say that you are at the entrance of an infinite Megastore. To know what products there are and which ones to take you will have to walk through countless lanes and choose what you need. An operation that could take an infinite amount of time if there are an infinite number of items.
Google, Bing and the other Search Engines do the same operation: they don't go there personally, but in the lane they send the so-called Spiders, who make an inventory of what's there and mark the routes to reach the different articles, so that they know where to find them when someone asks them.
The Web Crawlers, in fact, pass from one link to another of the different pages, in order to reconstruct the path that will return a clear mapping of the information.
What if your site is not yet in this huge virtual supermarket?
You're gonna have to bring that up. If the site is new and does not have any links connecting it to the network, this process cannot take place: you will have to request to be taken into consideration by sending the URL to Google via the Search Console.
Once learned of the presence of this new unexplored magical place, the Web Crawlers - as good explorers as they are - launch themselves into discovery. They analyze Tags, Metatag, Description, Copy, H1 and H2 and pass all the information to the search engine which, finally, will catalogue this new territory as a "digital marketing site" if it has found articles on the Paid Search, as "wine e-commerce" if it has found offers of Barolo or Ripasso di Valpolicella and so on.
When someone will want to stock up on their favorite wine and ask Google how to find it, they will receive - among other results - the new site's one. Whether search engines propose it in the first 5 results or on page 45 is then another topic that deserves a separate chapter. Whether the site is visible or hidden beyond the second page will depend on the so-called SEO (Search Engine Optimization).
What and how many Web Crawlers are there?
The most famous Web Crawler is certainly, and obviously, that of Google: Googlebot, which has many little brothers called Googlebot Images, Googlebot Videos, Googlebot News and AdsBot, dedicated to paid ads respectively.
There are others, of other search engines certainly less known but still important:
Yandex Bot, Spider of Yandex, Search Engine most famous and used in Russia;
Baiduspider for Baidu, the most important search engine in Chinese language;
Yahoo! Slurp for Yahoo!, who needs no introduction;
Bingbot, Bing's Spider, second largest search engine after Google and owned by Microsoft.
But does SEO have anything to do with Web Crawlers?
Yeah. Let's say it now and add another thing: SEO Matters, as Digital Specialists like to repeat (with good reason). SEO is the discipline that encompasses all the techniques that make Google select our site for a specific search (or Query) made by a user. And the Web Crawler then? It is our Personal Shopper who listens to our needs, goes to the lanes and selects the best product according to our requests. Important.
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