Crawling (Scanning)

Crawling (scanning) is the process by which search engine robots (crawlers) traverse web pages on the internet to collect data and add it to the search engine’s index.
Simply put, crawling is the first stage of a search engine’s work, where it examines a website to understand what it contains and how to present it to users.

What is Crawling?

Crawling is the automatic visiting and analysis of a website’s pages by a special program—a search engine robot (or bot, crawler, spider).
The robot follows links, reads page content (HTML code, text, images, meta tags, links) and sends this data to the search index.

Thus, without crawling, a website cannot appear in search engine results, because the search engine simply won’t know of its existence.

How the Crawling Process Works

1. Discovering new URLs. The search engine starts from known pages (e.g., from previous crawls, sitemaps, or external links).
2. Following links. The robot follows internal and external links, discovering new pages.
3. Extracting content. The bot downloads HTML code, images, meta tags, headings, descriptions, and other page elements.
4. Analyzing structure. It checks the site’s connectivity, navigation, content duplication, loading speed, and errors.
5. Sending data to the index. After successful crawling, the information is sent to the index—the search engine’s database from which search results are formed.

Example

When Google’s Googlebot crawls an online store’s website, it:

• finds the homepage;
• follows links to sections like “Catalog,” “About Us,” “Contacts”;
• reads product names, descriptions, prices, meta tags, and titles;
• adds new pages to Google’s index so they can be shown for user queries.

Types of Crawling

What Affects Crawling Quality

• robots.txt file. Controls robot access to pages—you can allow or disallow crawling of specific sections.
• Sitemap (sitemap.xml). Helps search engines find relevant pages faster and understand the site structure.
• Server response time. If a site loads slowly, the robot may interrupt the crawl.
• Internal linking. The better pages are interlinked, the easier it is for the robot to traverse the entire site.
• 404 errors and redirects. Excessive redirects and broken links hinder crawling.
• Duplicate content. Duplicate pages waste “crawl budget”—the limit of a robot’s visits to a site.

What is Crawl Budget?

Crawl Budget is the number of pages on a site that a search robot is willing to scan within a certain period.
The budget depends on:

• Site authority,
• Server stability,
• Content update frequency,
• Internal errors and redirects.
  If a site is large and slow, some pages may not get indexed because the robot won’t have time to crawl them.

Tools for Analyzing Crawling

• Google Search Console → “Crawl Status” report
• Yandex Webmaster → “Crawl statistics”
• Screaming Frog SEO Spider — desktop program for analyzing page structure and status.
• Sitebulb, Netpeak Spider, Ahrefs Site Audit — professional tools for SEO auditing.

How to Improve Site Crawling

• Configure robots.txt — allow indexing of important sections, block technical ones.
• Add sitemap.xml and update it when the site structure changes.
• Use internal links between important pages.
• Optimize page loading speed.
• Eliminate duplicates and broken links.
• Update content regularly—search engines crawl sites with new material more often.

Example of a Problem

If you accidentally specify in the robots.txt file:

text

Disallow: /

…then the robot won’t be able to crawl a single page of the site—and the resource will disappear from search results. Therefore, configuring this file requires special attention.

Conclusion

Crawling is a fundamental process of search engine optimization:
it’s at this stage that the search engine learns about a website’s existence, structure, and content.

Without proper crawling, it’s impossible to get into the index and rank in search results. That’s why SEO specialists always ensure that a site is accessible to robots, loads quickly, and is free of technical errors.