404 Checker: A Tool for Website Owners

Summary/Overview

The 404 Checker helps you verify that your website properly returns a hard 404 HTTP status for pages that don't exist. This feature ensures that Prerender.io doesn’t cache pages it shouldn't. Prerender caches every page with a 200 status code, so returning a 404 status on non-existing pages is important for SEO and your Prerender usage. Most of your monthly usage will come from cached pages being re-cached. Since soft 404 pages can accumulate in your cache over time, they can increase your monthly usage.

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

Detailed Explanation / How It Works

Hard vs. Soft 404

Hard 404: A properly configured 404 HTTP status code for non-existent pages. This page is not cached.
Soft 404: A non-existent page that shows an error message but incorrectly returns 200 OK. This causes the page to be cached and re-cached. Over time, they accumulate in your Prerender cache and increase your monthly usage.

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, which might increase your monthly usage.

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:

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. As the page is requested through Prerender, each check consumes a render.

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 crawlers (and Prerender’s cache system) treat the page correctly as a non-existent resource.

The soft 404 pages will be dropped from the cache upon recache once the above-mentioned meta tag is added to the head section of your non-existing pages, which should reduce your render usage.

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.