Fixing 'Lighthouse returned error' Messages in Site Kit by Google

If you're seeing a frustrating "Lighthouse returned error" message in your Site Kit by Google dashboard, you're not alone. Errors like ERRORED_DOCUMENT_REQUEST, FAILED_DOCUMENT_REQUEST, and NO_FCP are a common point of confusion for many WordPress users. This guide will explain what these errors mean and walk you through the most effective steps to resolve them.

What Do These Lighthouse Errors Mean?

It's important to understand that these errors are not generated by the Site Kit plugin itself. Site Kit acts as a dashboard that displays data from Google's PageSpeed Insights (PSI) tool. PSI, in turn, uses a tool called Lighthouse to analyze your website's performance. These errors occur when Lighthouse cannot successfully analyze your website. Common errors include:

• ERRORED_DOCUMENT_REQUEST / FAILED_DOCUMENT_REQUEST: Lighthouse could not load your website's URL. This is often due to a server-level issue, such as a 403, 404, 500, or 503 HTTP status code.
• NO_FCP: Lighthouse did not detect any content painting on the screen (First Contentful Paint). This can be caused by the browser tab not being in focus during the test or a problem with the page's render-blocking resources.

Most Common Causes and Solutions

Based on common community reports, here are the most effective troubleshooting steps to try.

1. Perform a Browser Test

Browser extensions, cached data, or other local factors can interfere with the Lighthouse test.

• Open a Chrome Incognito Window (or Firefox Private Window). This disables most extensions and uses a clean session.
• Navigate to your Site Kit dashboard and check if the error persists.
• If it works in Incognito mode, try disabling your browser extensions one by one in your normal browser to find the culprit.

2. Check Your Site's Health

Since these errors are often server-related, a problem with your WordPress installation could be the cause.

• Navigate to Tools > Site Health in your WordPress admin.
• Review the Status tab for any critical recommendations.
• Ensure your WordPress address and site address are correctly configured.

3. Test on the PageSpeed Insights Website

This is a crucial diagnostic step to determine if the issue is with Site Kit or with Lighthouse's ability to access your site.

• Visit the official PageSpeed Insights website.
• Enter your website's full URL and run an analysis.
• If the same error appears on the PSI website, the problem is environmental (your server/host) and not specific to the Site Kit plugin. If the analysis works on the PSI website but fails in Site Kit, it suggests a different conflict.

4. Investigate Server and Hosting Issues

As seen in the sample threads, moving to a new host is a frequent trigger for these errors. Contact your hosting provider and ask them to check for:

• Firewall Rules: Ensure that requests from Google's crawler bots (e.g., Googlebot) are not being blocked. A 403 status code often points to a block.
• Server Resources: A 500 or 503 error can indicate that the server is out of memory, has timed out, or has a misconfigured .htaccess file.
• ModSecurity Rules: Sometimes overzealous security modules can block legitimate analysis requests.

5. Perform a Site Kit Reset

If other steps point to a plugin-specific conflict, resetting Site Kit can help.

• Within your WordPress admin, go to Site Kit > Settings > Admin Settings > Reset Site Kit.
• This will clear its cached configuration and allow you to set it up again from scratch.
• Note: You will need to reconnect your Google services after this step.

When to Seek Further Help

If you have tried all the steps above and the error continues, the issue is likely specific to your server configuration. When seeking help in community forums, be prepared to provide your Site Health Info and details from the PageSpeed Insights test. This information is vital for others to help diagnose the problem effectively.