SEO Crawlers

SEO crawlers are tools that move through a website by following links, much like a search engine bot, and record technical data about every URL they find. They are used to spot problems such as broken links, redirect chains, missing titles and pages blocked from indexing.

Written by Paul Hoda, SEO consultant since 2005. Last updated 8 November 2026.

How SEO crawlers work

A crawler starts from a URL, usually the homepage, downloads the page, extracts its links and adds them to a queue. It repeats the process until it runs out of new URLs or hits a limit you set. For each URL it records details such as the status code, title, meta description, headings, canonical tag, directives, word count and internal links.

This mirrors how a web crawler such as Googlebot discovers pages, which is why crawl data is the backbone of most technical audits.

Desktop vs cloud crawlers

  • Desktop crawlers: software installed on your computer, such as Screaming Frog or Sitebulb. They are flexible and good value, but large sites are limited by your machine’s memory and must be run manually.
  • Cloud crawlers: services such as Lumar, JetOctopus or the site audit tools in Semrush and Ahrefs. They handle large sites, run on a schedule and make it easy to share reports, usually for a monthly fee.

What a crawl can reveal

  • Broken internal links and 404 errors.
  • Redirect chains, loops and links pointing to redirected URLs.
  • Missing, duplicate or overly long titles and meta descriptions.
  • Conflicting canonical tags and noindex directives.
  • Deep pages that take many clicks to reach, a measure known as click depth.
  • Pages with no internal links pointing to them, when crawl data is combined with sitemaps or analytics.
  • Large images, slow responses and other performance clues.

How to run a useful crawl

  1. Decide the scope: whole domain, a subfolder or a list of URLs.
  2. Choose the user agent, usually Googlebot smartphone, and decide whether to respect robots.txt.
  3. Turn on JavaScript rendering if the site relies on it for content or links.
  4. Connect Google Search Console, GA4 and your XML sitemap to find orphan pages and add traffic data.
  5. Set a sensible crawl speed so you do not overload the server.
  6. Export the issues, prioritise by impact and fix the biggest problems first.
  7. Recrawl after changes to confirm the fixes.

Limitations

An SEO crawler is not Googlebot. It does not know which pages Google has indexed, how often Google visits, or how Google chooses canonicals. Combine crawl data with Search Console and log file analysis to see how search engines actually behave on your site. Also remember that tool health scores are each vendor’s own invention: a score of 95 does not mean a site will rank well.

Key Takeaways

  • SEO crawlers follow links through a site and record technical data for every URL.
  • Desktop crawlers are flexible and cheap; cloud crawlers suit large sites and scheduled audits.
  • They find broken links, redirect problems, missing tags and deep or orphaned pages.
  • Enable JavaScript rendering and connect Search Console and analytics for richer results.
  • Crawl data shows what could happen, while log files show what Googlebot actually does.

Related Terms

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