Crawl Me Maybe? How Website Crawlers Work

There are roughly seven stages to web crawling:

When you publish your page (e.g. to your sitemap), the web crawler discovers it and uses it as a ‘seed’ URL. Just like seeds in the cycle of germination, these starter URLs allow the crawl and subsequent crawling loops to begin.

After URL discovery, your page is scheduled and then crawled. Content like meta tags, images, links, and structured data are downloaded to the search engine’s servers, where they await parsing and indexing.

Parsing essentially means analysis. The crawler bot extracts the data it’s just crawled to determine how to index and rank the page.

Also during the parsing phase, but worthy of its own subsection, is the URL discovery loop. This is when newly discovered links (including links discovered via redirects) are added to a queue of URLs for the crawler to visit. These are effectively new ‘seed’ URLs, and steps 1–3 get repeated as part of the ‘URL discovery loop’.

While new URLs are being discovered, the original URL gets indexed. Indexing is when search engines store the data collected from web pages. It enables them to quickly retrieve relevant results for user queries.

Indexed pages get ranked in search engines based on quality, relevance to search queries, and ability to meet certain other ranking factors. These pages are then served to users when they perform a search.

Eventually the entire crawl (including the URL rediscovery loop) ends based on factors like time allocated, number of pages crawled, depth of links followed etc.

Crawlers periodically revisit the page to check for updates, new content, or changes in structure.

As you can probably guess, the number of URLs discovered and crawled in this process grows exponentially in just a few hops.

Search engine crawling decisions are dynamic and a little obscure.

Although we don’t know the definitive criteria Google uses to determine when or how often to crawl content, we’ve deduced three of the most important areas.

This is based on breadcrumbs dropped by Google, both in support documentation and during rep interviews.

Offering a clear site structure via a logical sitemap, and backing that up with relevant internal links will help crawlers:

• Better navigate your site
• Understand its hierarchy
• Index and rank your most valuable content

Combined, these factors will also please users, since they support easy navigation, reduced bounce rates, and increased engagement.

Below are some more elements that can potentially influence how your site gets discovered and prioritized in crawling:

Web crawlers like Google crawl the entire internet, and you can’t control which sites they visit, or how often.

But you can use website crawlers, which are like your own private bots.

Ask them to crawl your website to find and fix important SEO problems, or study your competitors’ site, turning their biggest weaknesses into your opportunities.

Site crawlers essentially simulate search performance. They help you understand how a search engine’s web crawlers might interpret your pages, based on their:

• Structure
• Content
• Meta data
• Page load speed
• Errors
• Etc

If you want to scan entire websites in real time to detect technical SEO problems, configure a crawl in Site Audit.

It will give you visual data breakdowns, site health scores, and detailed fix recommendations to help you understand how a search engine interprets your site.

The Top Issues overview in Site Audit shows you your most pressing errors, warnings, and notices, based on the number of URLs affected.

Working through these as part of your SEO roadmap will help you:

1. Spot errors (red icons) impacting crawling – e.g.

• HTTP status code/client errors
• Broken links
• Canonical issues

2. Optimize your content and rankings based on warnings (yellow) – e.g.

• Missing alt text
• Links to redirects
• Overly long meta descriptions

3. Maintain steady visibility with notices (blue icon) – e.g.

• Organic traffic drops
• Multiple H1s
• Indexable pages not in sitemap

You can also prioritize fixes using filters.

Say you have thousands of pages with missing meta descriptions. Make the task more manageable and impactful by targeting high traffic pages first.

1. Head to the Page Explorer report in Site Audit
2. Select the advanced filter dropdown
3. Set an internal pages filter
4. Select an ‘And’ operator
5. Select ‘Meta description’ and ‘Not exists’
6. Select ‘Organic traffic > 100’

Segment and zero-in on the most important pages on your site (e.g. subfolders or subdomains) using Site Audit’s 200+ filters – whether that’s your blog, ecommerce store, or even pages that earn over a certain traffic threshold.

If you don’t have coding experience, then the prospect of crawling your site and implementing fixes can be intimidating.

If you do have dev support, issues are easier to remedy, but then it becomes a matter of bargaining for another person’s time.

We’ve got a new feature on the way to help you solve for these kinds of headaches.

Auditing your site with a website crawler is as much about spotting opportunities as it is about fixing bugs.

The Internal Link Opportunities report in Site Audit shows you relevant internal linking suggestions, by taking the top 10 keywords (by traffic) for each crawled page, then looking for mentions of them on your other crawled pages.

‘Source’ pages are the ones you should link from, and ‘Target’ pages are the ones you should link to.

The more high quality connections you make between your content, the easier it will be for Googlebot to crawl your site.

Understanding website crawling is more than just an SEO hack – it’s foundational knowledge that directly impacts your traffic and ROI.

Knowing how crawlers work means knowing how search engines “see” your site, and that’s half the battle when it comes to ranking.