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What is Crawling? Understanding Search Engine Operations and Web Crawlers

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Have you ever wondered how search engines discover countless web pages? At its core lies a process called crawling. To understand SEO, you need to know exactly what crawling is. So, what is crawling?

What is Crawling?​

Crawling is the process where search engine bots automatically visit websites and collect content. These bots are called crawlers, spiders, or bots, and in Google's case, they use a crawler named 'Googlebot'. Crawlers follow links on web pages to discover new pages and collect information.

Characteristics of Crawling​

  • Automated Process: Instead of humans manually visiting, programs automatically explore web pages.
  • Link-Based Navigation: Crawlers move by following links from one page to another.
  • Periodic Visits: They periodically revisit the same sites to discover new content or updated information.
  • Selective Crawling: They check the robots.txt file to visit only pages that website owners allow to be crawled.
  • Crawl Budget: Each website has an allocated crawl budget, so they don't crawl indefinitely.

Crawling Optimization Methods​

  • Configure robots.txt: Specify which pages crawlers can and cannot access through the robots.txt file.
  • Provide Sitemap: Provide an XML sitemap so crawlers can easily find all important pages.
  • Improve Internal Link Structure: Ensure all important pages are connected to other pages.
  • Improve Page Loading Speed: Slow pages waste crawl budget, so optimize speed.
  • Remove Duplicate Content: Duplicate pages make crawl budget usage inefficient.

Crawling Examples​

# robots.txt file example
User-agent: *
Allow: /
Disallow: /admin/
Disallow: /private/
Sitemap: https://example.com/sitemap.xml
<!-- Meta tags providing page information to crawlers -->
<head>
  <meta name="robots" content="index, follow">
  <meta name="googlebot" content="index, follow">
</head>

Actual crawling process:

  1. Googlebot visits the homepage
  2. Collects all links on the homepage
  3. Discovers new pages by following each link
  4. Collects content from discovered pages and sends to server
  5. Proceeds with indexing based on collected information

Crawling Advantages, Disadvantages, and Considerations​

Advantages​

  • Automatic Discovery: New content is automatically discovered by search engines.
  • Continuous Updates: Regular re-crawling keeps information up to date.
  • Extensive Coverage: Systematically explores all pages connected by links.

Considerations​

  • Crawling Blocks: Important pages may not be crawled due to robots.txt configuration mistakes.
  • Server Load: Excessive crawling can burden the server, so crawling speed should be controlled.
  • JavaScript Crawling Limitations: Some crawlers may not properly crawl content generated by JavaScript.

FAQ​

Q: What's the difference between crawling and scraping? A: Crawling is the process by which search engines discover and explore web pages, while scraping is the process of extracting specific data.

Q: How can I check if my site is being crawled? A: You can check in Google Search Console's crawling statistics report.

Q: Can I increase crawl frequency? A: If you frequently update high-quality content, submit sitemaps, and improve page speed, crawl frequency will naturally increase.

Crawling is the first step in search engine optimization. Since indexing and ranking are only possible when crawling is done properly, it's important to create a crawler-friendly website structure.