What Are Crawl Errors?
Common Types of Crawl Errors and Their Real-World Impact
Server errors, specifically the 5xx class of errors like the 500 (Internal Server Error) or 503 (Service Unavailable), are among the most critical. These indicate that the server hosting your website received a valid request from a crawler but failed to fulfill it due to an internal malfunction. This is comparable to a customer arriving at a store during open hours only to find the doors jammed shut. Common causes include excessive server load, faulty plugin or theme code, corrupted .htaccess file, or insufficient memory limits. For an e-commerce site, even a few minutes of 5xx errors during peak traffic can result in thousands of dollars in lost sales and severely damage brand credibility, as users quickly bounce to a competitor’s functioning site.
Client errors, the 4xx class, indicate that the requested page itself is problematic or missing. The most infamous is the 404 Not Found error, which means the server is working correctly but the specific page URL does not exist. This frequently happens when pages are deleted without proper redirection or when URLs are mistyped in internal or external links. While a few 404s are normal, especially on a large, aging site, a proliferation of them creates a poor user experience and wastes “crawl budget”—the limited number of pages a search engine bot will crawl on your site per session. Instead of discovering new, valuable content, the bot wastes time on dead ends.
Other technical errors include DNS errors, which mean the crawler cannot find your website’s server at all (like looking for a store that has moved without leaving a forwarding address), and robots.txt fetch errors, where the crawler cannot access the robots.txt file that instructs it on which pages to avoid. SSL certificate errors, like insecure HTTPS connections, also fall into a critical category as they directly impact security and user trust. Modern browsers explicitly warn users against visiting sites with such errors, and Google Chrome may even mark the entire site as “not secure,” causing a massive drop in legitimate traffic and conversions from security-conscious visitors.
Why Crawl Errors Matter: The Direct Impact on SEO and Revenue
The importance of resolving crawl errors cannot be overstated, as they directly corrode the foundation of your website’s search engine visibility. When a search engine bot cannot access a page, it cannot index its content. An unindexed page is invisible in search results, meaning it will never generate organic traffic no matter how well-optimized or valuable it is. This effectively nullifies your content marketing efforts. For a business relying on inbound leads, this is a direct leak in the pipeline. A critical service page or a flagship blog post returning a 500 error is as good as non-existent, silently crippling your marketing ROI and allowing competitors to capture the audience you worked hard to attract.
Beyond indexing, crawl errors severely damage the user experience (UX), which is a confirmed ranking factor. A visitor encountering a 404 or 500 error is likely to feel frustration and distrust, immediately bouncing back to the search results to click on a competitor’s link. This high bounce rate and low dwell time send negative quality signals to search engines, which can lead to a demotion in rankings for your functioning pages as well. Furthermore, if influential external sites have linked to a page that now returns an error, you are squandering valuable link equity and authority that could be boosting your domain’s overall ranking potential.
Finally, persistent crawl errors waste a precious resource known as crawl budget. For large sites with thousands of URLs, search engines allocate a limited number of pages they will crawl per visit. If bots are constantly getting stuck in dead ends like 404 loops or timing out on slow servers, they may leave before discovering and indexing your new, important content. This creates a significant competitive disadvantage, as your fresh content remains hidden while your competitors’ updated sites are crawled and indexed efficiently. Managing crawl errors is therefore not just about fixing old problems but about ensuring the future discoverability of your entire web presence.
A Practical Guide to Identifying and Fixing Common Crawl Errors
The first step in remediation is comprehensive identification. Google Search Console is your primary tool for this task. Within the “Indexing” section, you will find reports for “Pages” (showing indexed vs. non-indexed pages) and “Exclusions,” which often detail why pages are being excluded, including crawl errors. The legacy “Coverage” report is also invaluable, providing a graph and list of URLs experiencing errors, categorized by type (404, 500, etc.). For a more holistic site audit, premium tools like Ahrefs Site Audit or SEMrush Site Health can crawl your entire site like a search engine bot, providing a detailed list of technical issues including errors, redirect chains, and more.
Once identified, a systematic approach to fixing errors is crucial. For 404 errors, you have two main options. If the page is gone permanently and has no replacement, a 410 (Gone) status code can be used to tell search engines the deletion is intentional. However, if the page has simply moved or you have a relevant alternative, implementing a 301 redirect is the best practice. This permanently forwards users and link equity from the old, broken URL to a new, valid one. For server errors (5xx), the fix is more technical, often requiring collaboration with your hosting provider or developer to check server logs, increase resources, or debug faulty code.
To prevent new errors from cropping up, establish proactive maintenance routines. Before launching a site redesign or deleting old content, map all old URLs to new ones to ensure seamless 301 redirects. Use a broken link checker plugin on your CMS to scan for internal 404s. Finally, ensure your XML sitemap is updated and submitted to Search Console, acting as a direct map for crawlers to your most important pages. Consistent monitoring, perhaps on a weekly or monthly schedule, turns crawl error management from a frantic reactive process into a calm, proactive strategy for maintaining a healthy and visible website.
Essential Tools for Monitoring Your Website’s Health
While Google Search Console is the cornerstone of crawl error monitoring, a robust SEO strategy utilizes a suite of tools for a complete picture. These platforms offer deeper crawls, historical tracking, and competitor benchmarking that free tools often lack.
- Google Search Console: The essential, free starting point. It provides direct data from Google on crawl, index, and coverage issues. Its only limitation is that it only shows data for URLs that Google has already attempted to crawl.
- Ahrefs Site Audit: This tool performs a deep crawl of your entire site, mimicking a search engine bot. It excels at finding intricate issues like redirect chains, internal linking problems, and on-page SEO errors that contribute to poor crawlability.
- SEMrush Site Health: Similar to Ahrefs, it provides a site health score and detailed report on technical issues. It is particularly good at tracking changes over time and offering prioritized fixes based on their impact.
- Pingdom or GTmetrix: These tools focus on performance, which is indirectly related to crawling. Slow server response times can lead to crawl timeouts. They help you monitor uptime and speed, ensuring your server is always responsive to crawlers.
- Screaming Frog SEO Spider: A desktop-based crawler beloved by technical SEOs. It is incredibly fast and configurable, allowing you to crawl thousands of pages to quickly find broken links, review redirects, and analyze metadata at scale.
Crawl Error Priorities: A Data-Driven Response Table
The following table helps prioritize response efforts based on error type, impact, and common solutions. Addressing high-priority items first ensures you protect your most valuable assets: traffic and revenue.
| Error Type | Priority Level | Potential Impact | Recommended Action |
|---|---|---|---|
| 5xx Server Errors | Critical | Makes entire site or sections completely inaccessible, causing immediate traffic loss. | Contact your web host immediately; check server logs for specific error codes; disable recently added plugins/themes. |
| SSL/TLS Errors | Critical | Triggers browser security warnings, eroding user trust and blocking all secure traffic. | Renew or reinstall your SSL certificate; ensure your site forces HTTPS correctly. |
| 4xx on Key Pages | High | Important landing pages or product pages vanish from search results, hurting conversions. | Implement a 301 redirect to the most relevant live page or a custom 404 page with navigation options. |
| DNS/Timeout Errors | High | Prevents any user or bot from reaching your site, equivalent to a total outage. | Verify DNS settings with your domain registrar; investigate potential DDoS attacks with your host. |
| 4xx on Low-Value Pages | Medium | Wastes crawl budget and creates minor user friction, but does not impact core business. | Let them 404 or use a 410 status; ensure they return a sensible HTTP status code. |
Proactive Prevention: Building a Crawl-Error-Resilient Website
The best strategy for handling crawl errors is to prevent them from occurring in the first place. This involves building a stable technical foundation and implementing disciplined content management processes. Start with reliable, high-quality hosting; a cheap, overshared host is more prone to server overload and downtime, leading to frequent 5xx errors. Invest in a hosting solution that scales with your traffic and offers robust support. Furthermore, maintain a clean and logical site structure. A flat architecture, where important pages are just a few clicks from the homepage, makes it easier for crawlers to discover and index all your content efficiently, reducing the chance of orphaned pages that develop errors.
Content management is another critical area. Before deleting any page, assess its value. Check if it has any valuable backlinks using a tool like Ahrefs or SEMrush. If it does, always implement a 301 redirect to a relevant new page to preserve that link equity. For seasonal content or temporary promotions, consider unpublishing instead of deleting, or have a redirect plan ready from the outset. Implement a process for checking internal links, especially after making large-scale edits to your site. Many website maintenance guides recommend using a plugin or script to automatically scan for broken internal links on a regular schedule, catching errors before they multiply.
Finally, leverage the power of your robots.txt file and XML sitemap correctly. The robots.txt file should be used to block crawlers from low-value pages like admin scripts or thank-you pages, preserving crawl budget for important content. However, a single syntax error in this file can accidentally block all crawlers, so always use the tester tool in Google Search Console. Your XML sitemap should be automatically updated by your CMS whenever new content is published and promptly resubmitted to Search Console. This acts as an invitation for crawlers to efficiently discover your latest work, ensuring it gets indexed quickly and correctly, minimizing the window for potential errors to develop.
Crawl errors are far more than just technical glitches; they are critical symptoms of underlying issues that directly hinder your website’s ability to be found, used, and trusted. They silently strangle organic traffic, decimate user experience, and sabotage marketing investments. By understanding the different types of errors, utilizing the right tools to identify them, and implementing a disciplined process for fixes and prevention, you can eliminate these digital barriers. This proactive approach to technical SEO ensures that your website remains a healthy, accessible, and growing asset, fully capable of achieving its business goals and providing a seamless experience for every user and crawler that visits.