What is a Web Crawl? Important factors to know about Web Crawler 2023

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Web crawlers, web spiders or search engine bots are concepts that are not new to marketers or even web users.

What we often hear about web crawlers is the systematic task of browsing websites on the World Wide Web, helping to collect information about those web pages for search engines.

However, how web spiders work and how they affect the SEO process is not something everyone knows.

To find the answers to the above problems, please join me in reading the article below!

What is Crawl?

Crawl is data scraping (Crawl Data) is a term that is not new in Marketing, and SEO. Because Crawl is a technique that the robots of search engines use such as Google, Bing Yahoo…

Learn What is Crawl Data?

The main job of a crawl is to collect data from any page. Then proceed to analyze the HTML source code to read the data. And filter out according to user requirements or data that Search Engine requires.

What is Web Crawler?

Web crawlers, spiders or search engine bots are responsible for downloading and Indexing entire content from all over the Internet.

crawl là gì

Web crawlers

The word crawl in the phrase “Web crawlers” is a technical term used to refer to the automatic process of accessing websites and retrieving data through a software program.

The bot's goal is to dig through (almost) every page on a website to see what they're about; from there, consider retrieving information as needed. These bots are almost always operated by search engines.

By applying search algorithms to data collected by web crawlers, search engines can provide relevant links in response to users' search queries. Then create a list of web pages to display after the user enters a keyword in the search bar of Google or Bing (or another search engine).

However, the information on the Internet is so vast that it is difficult for the reader to know if all the necessary information has been properly indexed.

Is any information omitted?

So, to be able to provide all the necessary information, the web crawler bot will start with a set of popular web pages first; then follow the hyperlinks from these pages to other pages and to additional pages and so on.

In fact, there is no exact figure as to what percentage of websites displayed on the Internet are actually crawled by search engine bots. Some sources estimate that only 40-70%, or billions of websites on the Internet, are indexed for search.

How search engine bots crawl websites

The Internet is constantly changing and expanding. Since it is impossible to know the total number of websites on the Internet, web crawlers start from a list of known URLs. They first crawl webpages at those URLs. From these pages, they will find hyperlinks to many other URLs and add the newly found links to the list of pages to crawl next.

crawl data là gì

How it works

Given the large number of websites on the Internet that can be indexed for search, this process can go on almost indefinitely. However, the web crawler will follow certain policies that give it more choices about which pages to crawl, how it should be crawled, and how often to re-crawl for testing. content update.

The relative importance of each site: Most web crawlers do not collect all of the information that is publicly available on the Internet and do not serve any purpose; instead, they decide which pages to crawl first based on the number of other pages that link to that page, the number of visitors the site receives, and other factors that indicate its ability to provide information. important news of the site.

The simple reason is that if the website is cited by many other websites and has many visitors, it proves that it is likely to contain high quality, authoritative information. So it's easy for search engines not to index them right away.

Revisiting webpages:

Is the process by which web crawlers re-visit pages periodically to index the latest pieces of content because the content on the Web is constantly being updated, deleted or moved to new locations..

Requirements for robots.txt:

Web crawlers also decide which pages should be crawled based on the robots.txt protocol (also known as the robot exclusion protocol). Before crawling a site, they check the robots.txt file hosted by that site's web server.

The robots.txt file is a text file that specifies the rules for any bots accessing a hosted website or application. These rules define which pages bots can crawl and which links they can follow.

All of these factors are weighted differently according to the proprietary algorithms each search engine builds for their spider bots. web crawlers from Different search engines will behave slightly differently, although the end goal is the same: to download and index the same content from web pages.

Why are Web Crawlers called ‘spiders'?

crawler là gì

Bugs crawler

The Internet, or at least the part most users access, is also known as the World Wide Web – in fact, that's where the “www” part of most website URLs comes from.

It's completely natural to call search engine bots “spiders,” because they crawl all over the Web, like spiders crawling across a web.

What are the factors affecting Web Crawler?

The total number of active websites today amounts to millions worldwide. Are people satisfied with the current crawl and index rates? There are still many people wondering why their posts are not indexed.

So let's find out the main factors that play an important role in Google's crawling and indexing.


Google Panda was born to evaluate domain names, the importance of domain names has improved significantly. Domains that include the main keyword are rated well, and the website that is crawled well will also have a good ranking in the search results.


Quality backlinks make your website search engine friendly, trustworthy and quality. If your content is good, your website's ranking is also good, but without any backlinks, search engines will assume your website content is of poor quality.

Internal Links

Contrary to backlinks, Internal Links are links that lead to internal website articles. This is a must-have element when doing SEO, which is not only beneficial for SEO but also reduces website bounce rate, increases users' onsite time, and directs user access to other pages on your website.

XML Sitemap

Sitemap is essential for every website and it is very convenient that you can create it automatically. This helps Google index new articles or changes, updates as quickly as possible.

Duplicate Content

Duplicate content will be blocked by Google, this error can cause your website to be penalized and disappear from search results. Fix 301 and 404 redirect errors for better crawling and SEO.

Canonical URLs

Generate SEO-friendly URLs for each page on your website, which helps SEO while also supporting the website.

Meta Tags

Add unique, unmatched meta tags to ensure your website ranks high in search engines.

Should bots crawling websites be allowed to access web properties?

Bots crawl website
Whether web crawler bots should be able to access web properties no longer depends on what the web property is and a number of other factors attached.

The reason web crawlers request resources from the server is to get the basis of the content index – they make requests that the server needs to respond to, such as notifications when a user visits the website or other bots visit. to the website.

Depending on the amount of content on each page or the number of pages on the website, website operators consider whether to index searches too often, as too much indexing can crash the server, increase costs. bandwidth or both.

In addition, web developers or companies may not want to display certain websites unless the user has been provided with a link to the page.


A typical case is when businesses create a landing page specifically for marketing campaigns, but they don't want anyone not on the target audience's list to visit the page to adjust the message or measure. correct page performance.

In such cases, a business can add a “no index” tag to the landing page so that it does not show up in search engine results. They can also add a “disallow” tag in the page or in the robots.txt file so that search engine spiders won't crawl the page.

Web owners also don't want web crawlers to crawl part or all of their sites for a variety of other reasons.

For example, a website that provides users with the ability to search within the site may want to block search results pages, as these are not useful to most users. Other auto-generated pages that are only useful to a single user or a specific number of users will also be blocked.

Difference Between Web Crawling and Web Scraping

crawling và web scraping

Data scraping, web scraping or content scraping is the act of a bot downloading content on a website without the permission of the website owner, often with the intention of using that content for malicious purposes.

Web scraping is often more targeted than web crawling. Web scrapers may only track specific websites, while web crawlers will continue to track links and crawl pages continuously.

Besides, web scraper bots can bypass the server easily, while web crawlers, especially from the major search engines, will obey the robots.txt file and renew their requests so as not to type trick the web server.

How do “bugs” crawl the website?

Which to SEO?

SEO is the process of preparing content for the page, contributing to the page being indexed and displayed in the list of search engine results.

If the spider bot doesn't crawl a website, it obviously won't be indexed and won't show up in search results.

For this reason, if website owners want to get organic traffic from search results, they should not block bot crawlers.

What web crawling programs are active on the Internet?

The bots from the major search engines are commonly referred to as the following:

  • Google: Googlebot (there are actually 2 types of web crawlers on Google: Googlebot Desktop for desktop search and Googlebot Mobile for mobile search)
  • Bing: Bingbot
  • Yandex (Russian search engine): Yandex Bot
  • Baidu (Chinese search engine): Baidu Spider

Chương trình thu thấp web
There are also many less popular bot crawlers, some of which are not affiliated with any search engines so I'm not listing them in the article.

Why is bot management important to web crawling?
Bots are divided into 2 types: malicious bots and safe bots

Malicious bots can do a lot of damage from poor user experience, server crashes to data theft.

To block these malicious bots, allow secure bots, such as web crawlers, to access web properties.


Now you understand the importance of web crawlers to the performance and ranking of the website on search engines, right?

In general, to be able to crawl the website, you need to check if the website structure is stable? Are there any pages or the entire website blocking the crawling process? Is the page content guaranteed to be indexed?

Let's start editing so that the website always works best with search engine bots.

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