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What is a Web Crawler?

by | 29 Jun, 2022

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A web crawler, also known as a spider, is a program that visits websites and scrapes data: the content and the HTML structure.

This data then gets “summarized” and stored in a database called an index. Search engines use indexes to match relevant websites with user search queries (keywords). The same way librarians used catalog cards to find books.

Web crawler discovers new pages by following any links on the existing page to other pages. This process is repeated until the web crawler has visited all the pages on the website (ideally, the entire internet).

How Does A Web Crawler Work?

A web crawler works by visiting web pages and reading the data on the website. The crawler then follows links to other websites and reads the data on those websites.

This process is repeated until the crawler has visited all of the websites that it wants to visit.

Using Google Search Console for Your Search Results

If you want to see a list of all the web crawlers that have visited your website, you can use the Google Search Console.

To do this, simply login to your Google Search Console account and click “Settings”.

This will show you a list of all the Google crawls that have visited your website, as well as the date and time of their visit.

You can also see the number of pages that were crawled by each web SEO crawler.

What Are The Disadvantages Of Web Crawlers?

There are some disadvantages of web crawlers, including:

  • Can be slow
  • May miss some data
  • Can be blocked by websites

Why Are Crawlers Important To SEO?

Crawlers massively influence modern Search Engine Optimisation.


The first step in improving your website’s SEO is to make it more readable by crawlers. Websites that are easy to crawl will be favored over those that aren’t.

It will not only make your site easier to read for crawlers, but also for users if a site is easy to visit and navigate; and features the most important pages as few clicks from your home page as possible.

Moreover, if a website frequently crashes or is unavailable, this will also be noted by web crawlers and will result in a lower ranking.


Crawlers are also important for indexing new content. When you create new pages or blog posts, you need to ensure that they are indexed so that they can appear in SERPs. The best way to do this is to submit a sitemap to Google.

A sitemap is a file that contains a list of all the pages on your website. This makes it easier for crawlers to find and index new content.


Finally, web crawlers help to detect broken links. If there are broken links on your website, this will be noted by the crawler and will result in a lower ranking.

Examples of Crawlers

There are many different types of crawlers, but some of the most common include:

  • Googlebot: Google’s web crawler
  • Bingbot: Microsoft’s web crawler
  • YandexBot: Yandex’s web crawler
  • Baiduspider: Baidu’s web crawler
  • AhrefsBot: Ahref’s web crawler
  • DuckDuckGo: DuckDuckGo’s web crawler
  • Sogou Spider: Sogou’s web crawler

How Do I Stop A Web Crawler?

If you want to stop a web crawler from visiting your website, you can use a robots.txt file. This file tells the web crawler which pages on your website it should not visit.

Is There A Difference Between A Crawler And A Spider?

No — the word spider comes from the program crawling the web. A crawler may also be referred to as a robot or a bot.

What Is The Difference Between A Crawler And An Index?

When a website is being crawled, the web crawler will visit each page on the website and extract the content. This content is then added to an index.

An index, on the other hand, is a database of all the websites that have been crawled by the web crawler. When you perform a search on a search engine, the results come from the index.

Mihael D. Cacic
“Digital Marketing Mad Scientist”

Physicist turned SEO Content Marketer. For the past few years, Mihael worked with many big SaaS and service businesses helping them rank higher and get more customers. Now here to share his secrets on how to make hyper-profitable blogs in hyper-efficient ways.

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Founder, MailShake

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