Crawler

A crawler — also known as a spider or bot — is a type of automated program used by search engines to systematically browse the internet. The main job of a crawler is to find, scan, and index web pages, so they can be included in search engine results.

Think of a crawler as a robot that reads the web, page by page, following links and collecting data to help search engines like Google, Bing, and Yahoo organize the internet.

How a crawler works

1. Starts with known URLs – Crawlers begin with a list of known web addresses, such as those submitted through sitemaps or previously indexed pages.
2. Follows links – As the crawler visits each page, it follows internal and external links to discover new content.
3. Downloads page content – It reads the HTML, images, metadata, and other information.
4. Sends data back to the search engine – That information is stored and used to index the page.
5. Repeats the process – Crawlers revisit pages regularly to detect updates or changes.

Popular crawlers include:

• Googlebot – Used by Google
• Bingbot – Used by Bing
• DuckDuckBot – Used by DuckDuckGo
• YandexBot – Used by Yandex
• Baidu Spider – Used by Baidu

Why crawlers matter for SEO

If a crawler can’t access or understand your website, your content won’t be indexed — and that means it won’t appear in search results. Ensuring your site is crawler-friendly is a key part of technical SEO.

Good crawler access allows search engines to:

• Index your pages properly
• Understand the structure and hierarchy of your site
• Determine the relevance and value of your content
• Keep your search listings up to date

How to help crawlers

• Create an XML sitemap – This gives crawlers a roadmap of your site.
• Use a robots.txt file carefully – It can allow or disallow access to parts of your site.
• Avoid broken links and redirect loops – These waste crawl budget and block discovery.
• Keep your site structure clean and logical – Clear internal linking helps crawlers find all important content.
• Minimize heavy use of JavaScript – Some bots may not fully render or follow JS content.

Crawl budget

For larger sites, search engines allocate a crawl budget — the number of pages a crawler will scan within a certain time frame. Efficient site structure, fast load times, and no technical errors help you make the most of it.

In summary, a crawler is a search engine’s robot that explores the web to find and index content. Making your website easy for crawlers to access and understand is crucial for ranking in search engines and getting found by your audience.