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Why is my sitemap marked as “Unhealthy” or failing to crawl?

Prerender may flag a sitemap as unhealthy if it can’t be accessed, isn’t formatted correctly, or contains invalid URLs.

Overview

When submitting a sitemap to Prerender's crawler, you might see that it’s marked as Unhealthy in the dashboard. This status means Prerender either couldn’t crawl the sitemap itself or encountered problems with the URLs inside it.

This can prevent your pages from being prerendered and indexed properly, which may negatively impact SEO. It’s important to identify and fix the issue so the sitemap can be used to drive scheduled rendering operations.

Possible Causes / Scenarios

  • The sitemap URL is incorrect:
    Double-check that the sitemap URL is complete and publicly accessible.
  • Our crawler is blocked by a firewall:
    Your site might be blocking Prerender’s IP addresses or user agents.
  • The sitemap does not follow the proper XML format:
    Ensure the sitemap is valid according to the standard sitemap protocol. Common issues include:
    • Bad nesting of elements
    • Missing required tags like <loc>
    • Unsupported file formats
  • Sitemap contains broken or unreachable URLs:
    If one or more URLs return an error status (e.g., 404, 500), it can mark the sitemap as partially or fully unhealthy.
    • Check each listed URL to ensure it returns a 200 OK status
    • Use a tool like curl or your browser dev tools to validate response codes

Solution Steps / Troubleshooting Guide

  1. Verify the sitemap URL: Open it in your browser and ensure it's accessible.
  2. Test URL responses inside the sitemap: Each URL must return a 200 status code for the crawler to proceed.
  3. Validate the XML structure: Use a sitemap validator or the official protocol to check for formatting issues.
  4. Whitelist Prerender's IP addresses and user agents: Make sure nothing is blocking Prerender from accessing the sitemap and listed pages.

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Additional Tips / Best Practices

  • Keep your sitemap updated and free of broken links.
  • Limit each sitemap to 50,000 URLs or split into indexed sitemap files and a sitemap index.
  • Use Scheduled Rendering with validated sitemaps to automate re-caching for valid URLs.

When to Contact Support

If your sitemap is still marked unhealthy after corrections:

  • Send the sitemap URL to support@prerender.io.
  • Indicate the steps you’ve already tried (e.g., validation, firewall changes, etc.).
  • If possible, attach a screenshot of the status shown in the dashboard.

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