Crawling: SEO Explained

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Search Engine Optimization (SEO) is a multifaceted discipline that encompasses a wide range of strategies and techniques aimed at improving a website’s visibility in search engine results. One of the fundamental aspects of SEO is the process of crawling, which is the method by which search engines discover updated content on the web, such as new sites or changes to existing sites. Understanding how crawling works is crucial for anyone seeking to optimize their website for search engines.

Crawling is the first step in the process that allows search engines to collect and index information from across the web, making it available to users who are searching for relevant content. This glossary article will delve into the intricacies of crawling, explaining its role in SEO, how it works, and how website owners can optimize their sites for effective crawling.

Understanding Crawling

In the context of SEO, crawling refers to the process where search engines send out a team of robots, known as crawlers or spiders, to find new and updated content. Content can vary—it could be a webpage, an image, a video, a PDF, and more. Regardless of the format, crawlers scour the web to discover these content pieces.

These crawlers start by visiting a list of web addresses from past crawls and sitemaps provided by website owners. As they visit these websites, they use links on those sites to discover other pages. The crawlers then bring all those 1s and 0s back to the search engine to build an index. This index is then fed through an algorithm that tries to match all that data with your query.

The Role of Crawlers

Crawlers play a crucial role in SEO. They are the ones responsible for discovering new content or changes to existing content, allowing search engines to keep their search results up-to-date and relevant. Without crawlers, search engines would not be able to provide users with the information they are looking for.

Moreover, crawlers help search engines understand what your website is about. They analyze your site’s content, the meta tags, the titles, the images, and even the links between pages. This information is then used to determine when and where your website should appear in the search engine results pages (SERPs).

How Crawlers Work

Search engine crawlers follow links from one page to another and index everything they find on their way. As they move around the web, they focus on new sites, changes to existing sites, and dead links. When a crawler visits a webpage, it takes note of the page’s meta tags and its content. It then adds the HTML version of the page to the massive database known as the search engine index.

Once a page is in the index, it’s in the running to be displayed as a result to relevant queries. It’s important to note that crawlers cannot understand content the way humans do. Instead, they look for signals that indicate what the content is about. These signals include things like keywords, backlinks, and structured data.

Optimizing for Crawling

Optimizing your website for crawling is a crucial part of SEO. If search engine crawlers cannot access and understand your content, it won’t be included in the search engine index and, therefore, won’t appear in search results. There are several strategies you can use to ensure that your website is easily accessible and understandable to crawlers.

Firstly, make sure that your website is well-structured and easy to navigate. A clear and logical site structure will make it easier for crawlers to find and index your content. Secondly, use relevant keywords in your content. This will help crawlers understand what your content is about and how it should be categorized in the search index.

Using Robots.txt

The robots.txt file is a simple text file that tells search engine crawlers which pages or files the crawler can or can’t request from your site. This is used mainly to avoid overloading your site with requests; it is not a mechanism for keeping a web page out of Google. To keep a web page out of Google, you should use noindex directives, or password-protect your page.

Website owners should be careful when using the robots.txt file. If not used correctly, the file can block crawlers from accessing important parts of your website, which could result in those pages not being indexed. Therefore, it’s crucial to understand how to use the robots.txt file effectively.

Creating an XML Sitemap

An XML sitemap is a file where you can list the web pages of your site to tell Google and other search engines about the organization of your site content. Search engine web crawlers like Googlebot read this file to more intelligently crawl your site.

Having an XML sitemap can be beneficial for SEO, as it allows Google to quickly find your essential website pages, even if your internal linking isn’t perfect. This is important because Google and other search engines indexes web pages, not just websites. So the more pages your site has indexed, the more likely you are to drive organic traffic to your site.

Common Crawling Issues

While the process of crawling is automated and systematic, it’s not without its issues. There are several common problems that can prevent crawlers from accessing and indexing your content. Understanding these issues can help you troubleshoot any problems and ensure that your website is being crawled effectively.

Some of the most common crawling issues include blocked resources, which are elements of your website that are blocked from crawlers; crawl errors, which occur when a crawler cannot access a webpage; and duplicate content, which can confuse crawlers and lead to indexing issues.

Blocked Resources

Blocked resources are parts of your website that are blocked from search engine crawlers. This can include things like images, CSS files, and JavaScript files. If these resources are blocked, it can prevent crawlers from fully understanding your webpage, which can impact how your page is indexed and ranked in search results.

To avoid this issue, make sure that all important resources are accessible to crawlers. You can check for blocked resources in Google Search Console, which provides a report of any resources on your site that are blocked to Googlebot.

Crawl Errors

Crawl errors occur when a search engine crawler tries to reach a page on your website but fails. This can happen for a variety of reasons, such as a server error, a broken link, or a page that no longer exists. Crawl errors can prevent your page from being indexed and appearing in search results.

To fix crawl errors, you need to first identify them. You can do this using Google Search Console, which provides a report of any crawl errors that Googlebot has encountered on your site. Once you’ve identified the errors, you can then take steps to fix them, such as repairing broken links or fixing server issues.

Duplicate Content

Duplicate content refers to substantial blocks of content within or across domains that either completely match other content or are appreciably similar. Mostly, this is not deceptive in origin. However, search engines don’t know which version(s) to include/exclude from their indices, whether to direct the link metrics to your page, or another, or how to rank multiple versions with regards to search results.

To prevent duplicate content issues, make sure that each page on your website has unique content. If you have multiple pages with similar content, consider merging them into one page. You can also use canonical tags to tell search engines which version of a page you want to be considered the original.


In conclusion, understanding and optimizing for crawling is a fundamental part of SEO. By ensuring that your website is easily accessible and understandable to search engine crawlers, you can improve your site’s visibility in search results and drive more organic traffic to your site.

Remember, SEO is a long-term strategy, and while it may take time to see results, the effort is well worth it. By understanding how crawling works and how to optimize for it, you can set your website up for success in the world of search.


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