Crawl Errors Explained: How to Find and Fix Every Type
Crawl errors are problems that Googlebot encounters when attempting to access, crawl, or process pages on your website. These errors prevent proper indexation and can significantly limit your organic search visibility. Understanding each error type, its cause, and its fix is foundational technical SEO knowledge.
This guide covers every category of crawl error you'll encounter in Google Search Console and Screaming Frog, along with prioritized fixes.
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Understanding Crawl vs. Index vs. Rank
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Before diving into specific errors, distinguish between three separate processes:
Crawling: Googlebot discovers and fetches your page's HTML (and resources)
Indexing: Google processes the crawled content and decides whether to add it to its index
Ranking: Google determines where indexed pages rank for relevant queries
Crawl errors disrupt the first step — if Google can't successfully crawl a page, it can't index or rank it. Some crawl errors affect resource loading (images, scripts) without preventing indexation; others prevent the page from being indexed at all.
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Where to Find Crawl Errors
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Google Search Console — Coverage Report:
GSC's Coverage Report (Index > Coverage) is the primary source of crawl and indexation errors. It categorizes URLs into:
Error: Pages that couldn't be indexed due to an error
Valid with warning: Pages that are indexed but have issues
Valid: Successfully indexed pages
Excluded: Pages intentionally excluded from the index
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Each category expands to show specific error types with affected URL examples.
Google Search Console — URL Inspection Tool:
Test any specific URL to see Googlebot's current perspective: last crawl date, rendered HTML, any coverage or indexation issues.
Screaming Frog:
Crawls your site from a bot's perspective, capturing every HTTP status code. The Response Codes tab sorted by status code gives a complete picture of your crawl error landscape.
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HTTP Status Code Errors
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404 Not Found:
The most common crawl error. The requested page doesn't exist on the server.
*Causes:*
Pages deleted without implementing a redirect
Internal links pointing to changed URLs
External links to pages that no longer exist
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*Fix:*
For pages with significant traffic or backlinks: create 301 redirects to the most relevant existing page
For pages with no traffic or backlinks: leave as 404 (don't create unnecessary redirects)
Update internal links to remove the 404 reference
If the page should exist: restore it
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*Finding them:*
GSC Coverage > Error > Not found. Screaming Frog > Response Codes > 4xx.
410 Gone:
Explicitly signals that a page has been permanently removed. More definitive than 404 for pages you've intentionally deleted.
*When to use 410 vs. 404:*
410 tells Google the resource is intentionally gone permanently. For expired promotions, discontinued products, or removed content, 410 is marginally more explicit. For most use cases, 404 is functionally equivalent.
500 Internal Server Error:
The server encountered an unexpected condition. Google will retry these pages but may eventually drop them from the index if errors persist.
*Causes:*
PHP or application errors
Database connection failures
Plugin conflicts (WordPress)
Server resource exhaustion
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*Fix:*
Check server error logs immediately. Common fixes include: restarting database services, disabling problematic plugins, increasing memory limits, or contacting your hosting provider.
503 Service Unavailable:
Server temporarily unable to handle requests, typically during maintenance or overload.
*Best practice for maintenance:*
Return 503 with a Retry-After header during planned maintenance. This tells Google the downtime is temporary and to try again, rather than treating the pages as gone.
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URL/Redirect Errors
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Redirect Error:
Google followed a redirect that itself returned an error status — the redirect destination returned a 404, 500, or another error code.
*Fix:* Check the destination URL of the redirect. Update the redirect to point to a valid, 200-returning URL.
Redirect Loop:
A URL redirects to itself or creates an infinite chain: A→B→C→A.
*Fix:*
Use Screaming Frog's Redirect Chain report to identify loops. Fix by breaking the loop — choose the correct canonical destination and redirect all other URLs directly to it.
Redirect Chain:
Multiple sequential redirects: A→B→C→D. Not an error that prevents indexation, but wasteful. Each hop in the chain adds latency and reduces link equity transfer.
*Fix:*
Update all redirects to point directly to the final destination URL. A→D, B→D, C→D.
URL has crawl issue:
A catch-all error in GSC for URLs that couldn't be reached due to connection timeouts, DNS resolution failures, or other network-level issues.
*Fix:*
Check server uptime and DNS configuration. Investigate server error logs for patterns in when these errors occur.
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Robots.txt Blocked
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Blocked by robots.txt:
GSC reports URLs that Googlebot is not allowed to access based on your robots.txt Disallow rules. These are not necessarily errors — you may have intentionally blocked certain sections.
*When this is an error:*
When important pages or critical resources (CSS, JavaScript, images) needed to render pages are blocked.
*Fix:*
Review your robots.txt and check whether the blocked URL should be accessible. If blocked pages should be indexed, remove the blocking rule. If CSS/JS is blocked and preventing rendering, add Allow: /path/to/resource rules.
*Critical warning:*
Never add Disallow: / to robots.txt on a live production site unless you intend to block all search engine crawling. This is one of the most devastating technical SEO errors possible.
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Noindex Issues
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Submitted URL marked 'noindex':
GSC reports pages in your submitted sitemap that have a noindex meta robots tag. This creates a contradictory signal — your sitemap suggests you want them indexed, but the tag says you don't.
*Fix:*
Either remove the noindex tag (if the page should be indexed) or remove the URL from your sitemap (if the noindex is intentional).
*Common cause:*
Development environments with sitewide noindex that wasn't removed before launch. Or CMS settings that were misconfigured.
Excluded by 'noindex' tag:
GSC's Excluded section shows pages that have been excluded from the index because of noindex tags. This is normal and expected for admin pages, thank-you pages, and other non-indexable content. It becomes an issue only if important pages appear here that should be indexed.
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Crawl Budget Issues for Large Sites
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Crawl budget is the number of pages Googlebot crawls on your site within a given timeframe. For large sites (100,000+ pages), crawl budget limitations can prevent important new content from being indexed promptly.
Signs of crawl budget problems:
New pages taking days or weeks to appear in the index
Old, low-value pages being crawled repeatedly while new pages aren't crawled
Coverage report showing many "Discovered - currently not indexed" pages
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Causes of crawl budget waste:
Faceted navigation generating thousands of URL combinations
Session IDs creating unique URLs per visitor
Infinite calendar pages
Printer-friendly page variants without canonical tags
Low-value paginated pages (page 50, page 100 of thin content)
Redirect chains that require multiple fetches
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Fix crawl budget issues:
Disallow or noindex URL patterns that consume crawl budget without indexation value (via robots.txt or meta robots)
Use canonical tags consistently on parameterized URLs
Ensure your XML sitemap contains only canonical, valuable URLs
Improve site speed to allow Googlebot to crawl more pages per visit
Increase internal linking to important new pages so Googlebot discovers them through followed links
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Monitoring and Resolving Crawl Errors Systematically
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Priority order for fixing:
500 errors (server problems — fix immediately)
Blocked critical resources (CSS/JS blocked in robots.txt)
404 errors with backlinks or internal links pointing to them
Noindex on important pages
Redirect chains and loops
404 errors with no backlinks (lower priority)
Crawl budget issues (for large sites)
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Setting up alerts:
GSC doesn't have native email alerts for individual crawl errors, but Screaming Frog can be configured for automated scheduled crawls with email alerts. Third-party monitoring tools like ContentKing provide real-time crawl error detection.
Blakfy conducts crawl error audits as part of comprehensive technical SEO engagements, using Screaming Frog combined with GSC data to identify and prioritize all error types by business impact.
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Frequently Asked Questions
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How many 404 errors are acceptable?
Every site accumulates some 404s from deleted pages, external link rot, and user typos. The key question is whether any 404 pages have backlinks or internal links pointing to them — those have clear SEO value to recover through redirects. 404s with zero external links and no internal links have minimal ranking impact. Monitor regularly and focus remediation effort on 404s with link equity to recover.
Will crawl errors directly hurt my rankings?
Crawl errors on important pages directly prevent those pages from being indexed — which prevents them from ranking entirely. Crawl errors on low-value pages have minimal impact. 500 server errors that persist cause Google to trust your site less and may reduce crawl frequency across the entire domain. Fixing critical crawl errors is therefore a prerequisite for ranking, not just a cleanup task.
How do I check if my robots.txt is blocking important pages?
Use the Robots.txt Tester in Google Search Console (Legacy Tools > Robots.txt Tester). Enter specific URLs to check whether your current robots.txt allows or blocks Googlebot access. Also check the URL Inspection Tool for specific pages — it explicitly states whether a page is blocked by robots.txt.
