What is crawling?
Crawling is the process in which search engines' automated programs, often called web crawlers or spiders, systematically work through the internet to discover and fetch new and updated content on websites. Where indexing is about storing and organising pages for search results, crawling is about finding them in the first place. This means that without proper crawling, a page can't even be considered for display in search results.
Search engines such as Google or Bing typically start with a list of known URLs and follow links from page to page. When a crawler loads a page, it reads the HTML code, registers links, metadata and content, and from there decides which pages to visit next. The process resembles how you click your way around the web yourself — the difference is simply that the crawler does it far faster and more systematically.
Crawling acts as the search engine's eyes and ears. It doesn't just register content, but also technical signals that help the algorithm understand quality and structure. That's why a large part of technical SEO is precisely about making sure the crawler can access and understand your website correctly. It covers everything from creating a clear internal linking structure to optimising speed and mobile-friendliness, as slow pages or blocks in robots.txt can slow crawling down.
How do you use your knowledge of crawling?
When you work with SEO, you can use your understanding of crawling to optimise how search engines find and prioritise your content. That requires you to take control of the parts of your website that guide the crawler's behaviour. Information architecture, navigation and internal links all play a role here, because together they form the network the crawler follows.
Your knowledge of crawling also helps you judge when to ask Google to revisit a page. That might be, for example, when you've updated a product, added new content or changed the page's structure. You can use Google Search Console or SEO tools to monitor how Googlebot interacts with your site – and so spot whether there are pages that aren't being crawled at all.
In other words, it's about giving search engine bots the best possible access to your content. If you combine this insight with, for example, digital design or content production, you can not only improve loading speed and structure, but also create content that the search engine can more easily understand and present to users.
Why do you need to know about crawling?
You need to know about crawling because it's the foundation for your website appearing in search results at all. Without crawling, your pages are invisible to search engines — and therefore to users too. Once you understand the process, you can identify obstacles that disrupt the search engines' work, such as broken links, missing redirects or inaccessible resources.
Crawling also affects how quickly new content shows up in search results. If your website is crawled often, search engines quickly discover changes and updates. That gives you a significant advantage when you work continuously with content marketing, because fresh and relevant content can gain visibility faster. At the same time, a well-designed URL structure and up-to-date sitemaps make it easier for the crawler to keep up with new pages and versions.
You can also use crawling as a kind of technical health check. An SEO crawler shows you how a bot experiences your website. That way, you can discover non-indexed areas, overly complex menus or resources blocked by errors in robots.txt. It gives you concrete insights for improving both visibility and user experience.
What types and variants are there?
There are several related concepts you should know when you work with crawling. The first is crawl budget — the amount of time Google allocates to your website during a crawling session. Google allocates the budget based on how important or popular the site is judged to be, and how often the content changes. If your website has thousands of pages but a poor structure, for example, it may mean that only some of them get crawled.
Another important concept is crawl depth, which describes how many clicks a crawler has to take from the homepage to reach a particular subpage. The deeper a page sits in the structure, the less likely it is to be crawled. This makes it clear why internal link structure and navigation matter so much for SEO – they help the crawler find its way without “getting lost”.
How do you handle crawling in practice?
To get the full benefit of crawling, you need to work actively at making your website easy to crawl. A good start is keeping an up-to-date XML sitemap and making sure all important URLs have internal links. If you're working with a larger site, you can use tools such as Screaming Frog, Sitebulb or Search Console to test how a crawler reads the structure. That gives you an overview of any barriers and errors.
In practice, you should also use robots.txt with care. It mustn't block pages you actually want search engines to find. Likewise, you should check canonical tags to avoid duplicate content that can confuse crawlers and waste crawl budget. If you publish often, you can ask Google to re-crawl pages so changes are picked up more quickly.
Crawling is also closely linked to performance. Pages that load quickly and have a clear internal structure are prioritised higher. This means that work on technical SEO — from speed optimisation to mobile-friendly design — affects how efficiently your pages are crawled and indexed. In this way, crawling becomes not just a technical topic, but a central part of the overall digital strategy.
What should you watch out for?
You should pay particular attention to how changes in structure, technology or CMS can affect crawling. When you redesign pages or switch domains, you risk losing existing links, and with them crawl access to certain areas. That's why it's important to test new pages in staging environments or use tools to simulate how bots navigate the final version.
Another point to focus on is orphan pages — pages that have no internal links and therefore aren't discovered by crawlers at all. It's a typical challenge if, for example, you create landing pages for campaigns or ads but don't tie them in with the rest of your website. By building in a strategic linking structure, you prevent relevant content from falling outside the search engine's map.
Finally, remember that crawling doesn't happen constantly. Search engines prioritise and schedule their crawl activity on an ongoing basis. That's why it makes sense to monitor your crawl log files, so you can see exactly which pages are visited and how often. It's a valuable way to understand how search engines actually see your website — and so how you can make their job easier.
