What is a web crawler and what is it used for?

What is a web crawler and what is it used for?


In the immensity of the web ecosystem, the contents of web pages are sorted in order to be offered to users. To appear in search engine results pages, they are analyzed from top to bottom by “web crawlers”. These small robots are programmed to browse the various documents present on the web and collect them to form a database.

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Understanding how crawlers work is essential for SEO strategies. Here is what there is to know about indexing robots.

What is a crawler used for?

Search engines were created to provide an answer to a problem of the Internet user, according to a typed request. They bring together a large number of websites, like a virtual library. They do not require any human intervention to be enriched regularly, it is automated. Like librarians, indexing robots will therefore scan all existing sites and content.

The main objective of a crawler is then the collecting information for the purpose of creating an index, in other words a database. To do this, robots examine the web in search of content to offer results to Internet users. They automatically browse the hypertext links of the pages and return to visit those already explored to check if they have been modified.

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A crawler allows to index web pages depending on the quality of the content offered, to help search engines establish a ranking in the search results (SERP). It participates in providing the most relevant answers to Internet users according to their request.

They use different criteria to determine the quality of the pages. Constantly evolving, these factors relate to keywords, content, site structure, internal and external networking, general site navigation and many others. To help crawlers explore the site, it is necessary to have a good tree structure and simplified navigation, as well as a sitemap.

The mission of a bot is therefore to ensure the relevance of the content of the sites and exclude unnecessary web pages from the index. It is essential in SEO strategies, both to position pages in the SERPs, and to audit a site for optimization. It will make it possible to highlight the structural elements to be revised to improve the positioning.

The different types of crawlers

There are several categories of spider, with slightly different objectives from each other.

First, there is the indexing crawler. This is the oldest. It is used by search engines and helps to rank pages on the internet. It is important because it determines the appearance in the search results. The most popular is that of the search engine giant: the Googlebot.

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In the event that a site blocks the exploration of crawlers, it loses all chances of being visible in the results pages, because it will not be indexed. Depending on the natural referencing strategy, it may be wise not to index certain content within a site.

Then there is the diagnostic crawler. It is an analytical tool that is used to help with natural referencing (SEO). It allows you to perform a complete SEO audit by highlighting faults and areas for improvement. It thus analyzes the structure of the site, the access to the pages, the number of URL links, the loading time, the internal mesh, the source codes, the presence of duplicate content, and any problems it may have encountered. It is used to provide optimizations to a site. It is an essential procedure to ensure the health of a website and improve its natural referencing.

There is also the standby crawler, which makes it possible to follow the evolution of a market. As its name suggests, it allows competitive intelligence and the recovery of data relating to product prices (data mining).

In some areas, spiders are also used to collect e-mail or postal addresses of companies.

How does a crawler work?

First of all, you should know that a crawler consists of a code with scripts and algorithms. He therefore responds to specific tasks assigned to him. Indexing robots rake automatically, 24 hours a day, web pages and hypertext links.

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Its operation is simple: it finds a page, explores it, saves it, follows the links it detects to find other pages, saves them, follows new links and so on. It always begins its exploration with known URLs.

When a robot arrives on a website, it first performs a crawl phase. This is the very first step in the process of positioning in the SERPs. It will then analyze all the elements constituting a web page to inform the proposed content. It collects both text, images, links, tags and titles; hence the importance of clearly indicating them for SEO positioning.

The spider also checks if it already knows this page. If it has browsed it in the past, it inspects the changes to see if it is a newer version. If so, then the page is automatically updated in the index.

Following this crawl step, the page is indexed by the search engine. It can therefore be offered to Internet users according to their request.

In the case where the content of a page does not have to be indexed, a “noindex” meta tag can be placed in the HTML code. This prevents bots from crawling the page and indexing it in search results.

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