What is an SEO Crawler? (And How to Use One)
An SEO crawler visits every page on your site and records what a search engine sees. Here is how they work, what they find, and how to get the most from one.
13 May 2026 · 6 min read
An SEO crawler is a tool that automatically visits every page on a website, follows its links, and records data about each page as it goes. The result is a structured dataset of the entire site, showing how each page looks to a search engine - response codes, metadata, link structure, images, and more.
The term "crawler" comes from the programs search engines use to discover and index content. Google calls its crawler Googlebot. Bing uses Bingbot. SEO crawlers work the same way, but they are designed to be used by website owners and marketers rather than by search engines themselves.
How an SEO crawler works
An SEO crawler starts at a seed URL - usually the homepage. It fetches that page, parses the HTML, and extracts every internal link it finds. It then visits each of those linked pages, extracts their links, and continues the process until it has visited every reachable page on the site or hit a configured limit.
At each page, the crawler records:
- The HTTP response code (200, 301, 302, 404, etc.)
- The page title
- The meta description
- The H1 tag
- Any canonical tag
- The robots meta tag (noindex, nofollow, etc.)
- Every outbound link, with anchor text
- Every image, with its src and alt attribute
- Response time
- Page size and word count
This data is then analysed to identify issues.
What an SEO crawler finds
An SEO crawler does not make assumptions. It reports what the server actually returns. This makes it the most reliable source of technical SEO information available, because it sees exactly what Googlebot sees when it visits the same URLs.
Common issues a crawler surfaces:
- Broken pages - pages returning 404, 410, or 500 errors
- Redirect chains - A redirects to B which redirects to C, wasting crawl budget
- Missing title tags - pages with no
<title>element - Duplicate title tags - multiple pages sharing identical titles
- Missing meta descriptions - pages with no meta description
- Duplicate meta descriptions - multiple pages sharing the same description
- Missing H1s - pages with no H1 heading
- Non-indexable pages - pages blocked by noindex, canonical issues, or robots.txt
- Missing alt text - images without an alt attribute
- Hreflang errors - incorrect or missing international targeting tags
- Security header issues - missing HSTS, CSP, or X-Frame-Options headers
SEO crawlers vs search engine crawlers
Search engine crawlers index the web. SEO crawlers audit a specific site. The difference in purpose matters:
- Googlebot prioritises pages based on crawl budget and site signals. An SEO crawler visits every page on the site regardless of priority.
- Googlebot's data is not directly visible to you. An SEO crawler's data is fully accessible.
- Googlebot reflects the state of your site over time, based on its crawl schedule. An SEO crawler gives you a snapshot of the current state, on demand.
Running an SEO crawl gives you a view of your site that is more current and more complete than anything available through Google Search Console.
Why crawl budget matters
Search engines have a finite amount of time to spend crawling each site. For large sites, Googlebot cannot crawl every page on every visit - it prioritises pages based on how important and frequently updated they appear to be.
Broken pages, redirect chains, and large amounts of non-indexable content all waste crawl budget. If Googlebot spends time on error pages and unnecessary redirects, it has less time to crawl and index the pages that actually matter.
An SEO crawler helps you identify and eliminate crawl budget waste. See also: What is Crawl Budget and Why Does It Matter?
SEO crawlers and internal linking
An SEO crawler maps the complete internal link structure of a site. This makes it possible to identify:
- Orphan pages - pages with no internal links pointing to them, making them invisible to crawlers that follow links
- Thin internal linking - important pages that only have one or two internal links pointing to them
- Over-linking to non-priority pages - homepages and category pages that link extensively to low-value pages
Internal link structure is one of the most controllable factors in SEO. A crawler makes the current state of that structure visible.
Crawly: a free SEO crawler for Mac
Crawly is a free native macOS SEO crawler. It crawls unlimited pages, stores all data locally, and surfaces issues across 19 categories automatically. There is no page cap, no subscription, and no requirement to create an account.
Crawly also includes a crawl comparison feature for diffing two crawls side by side, a Claude Code MCP integration for querying crawl data in plain English from your terminal, and a free SEO spider page with more detail on how it works as a desktop crawler. For a deeper look at what SEO spider software is and how it works, see what is SEO spider software.
For a comparison with other crawlers, see:
How often should you crawl?
- Monthly is a reasonable baseline for most sites. It catches issues that have accumulated since the last audit.
- After every significant deploy - a site rebuild, URL restructure, or CMS migration should always be followed by a crawl.
- Weekly for high-velocity sites that publish frequently, have large editorial teams, or undergo regular structural changes.
The more your site changes, the more frequently you should crawl it.
An SEO crawler is the most direct way to understand how search engines see your site. For a full list of free tools to use alongside a crawler, see the best free SEO tools guide.
Download Crawly and run your first crawl for free.