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404 Checker: A Tool for Website Owners

Ensure that non-existent pages on your site return the correct 404 status code to protect your SEO and caching accuracy.

Summary/Overview

The 404 Checker helps you verify that your website correctly returns a hard 404 HTTP status for pages that don't exist. This tool is essential for SEO and ensures that Prerender.io doesn’t attempt to cache pages that shouldn't be indexed. Only pages that return a 200 status are cached by Prerender, making it critical to distinguish between valid pages and errors using proper headers.

This tool helps website owners and developers validate error handling across multiple domains—and fix soft 404s that can confuse bots and damage SEO.

 

Detailed Explanation / How It Works

Hard vs. Soft 404

  • Hard 404: A properly configured 404 HTTP status code for non-existent pages. Caches properly ignore these.
  • Soft 404: A non-existent page that shows an error message but incorrectly returns 200 OK. This causes broken pages to be cached and indexed.

Why It Matters for Prerender

The Prerender service does not interpret content visually—it relies on HTTP status codes alone. To prevent caching of invalid or error pages, only pages returning HTTP 200 are stored. If your site returns a 200 for a page that doesn’t exist (soft 404), Prerender may cache content that it shouldn’t.

 

Step-by-Step Usage

1. Add Your Domain

In the 404 Checker interface, add your domain to begin regular checks. The tool will analyze error response behavior for that domain.

2. Understand the Verification Behavior

When a domain is added:

  • A question mark icon appears in the “Domain Reachable” and “404 Status Returned” columns while verification is in progress.
  • Once verified, a checkmark will appear if the site is reachable and a proper 404 status is detected for bogus URLs.

3. Warning for Soft 404s

If your site shows content on a fake page but returns 200 instead of 404, the 404 Checker displays a warning icon. Hover over the icon to see a tooltip such as:

image-1695795061231

This indicates a soft 404 and that search engines or crawlers may misinterpret the page as valid.

4. Set a Check Interval

You can choose how often to run this validation per domain, ranging from:

  • Every 1 hour
  • Every 4 hours
  • Every 8 hours
  • Every 24 hours (Default)
  • Every week

Note: Increasing check frequency may result in additional rendering costs depending on your plan.

 

How to Fix a Soft 404

Use the prerender-status-code meta tag to force Prerender to return a proper 404 response to search bots—even if your backend returns 200 for human users.

<meta name="prerender-status-code" content="404">

This does not affect what human visitors see, but ensures bots (and Prerender’s cache system) treat the page correctly as a non-existent resource.

Common Pitfalls / Tips

  • Always return a 404 status from your server or use the prerender tag to override soft 404s.
  • Check your verified domains periodically.
  • High-frequency checks (1–8 hours) should be reserved for larger sites or during deployments.

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