Why am I seeing 403 or 404 errors after integrating Prerender?
Common causes for these errors after integration — and how to fix each one.
TL;DR
After integrating Prerender, 403 errors usually mean your firewall is blocking Prerender's crawler or the Prerender token is missing from your integration. 404 errors usually mean the URL rewrite in your integration is incorrect, the URL doesn't exist, or an ignore filter is blocking it. Both error types are fixable from your Prerender dashboard and your server or CDN configuration — the sections below cover each cause and fix.
Why this matters
403 (Access Denied) and 404 (Not Found) errors mean Prerender's crawler can't successfully fetch or access the requested pages. When this happens, AI crawlers and search engines like GPTBot, ClaudeBot, and Googlebot receive errors instead of your fully rendered HTML — which means your content may not be indexed and your AI citations and search rankings may suffer.
Fixing these errors quickly restores the flow of clean HTML to crawlers, so your pages stay readable, indexable, and citable.
403 errors: access denied
A 403 means your server or firewall is actively refusing Prerender's crawler request. Two causes are responsible for almost every 403 we see.
Cause 1: Prerender's IP addresses are blocked or rate-limited
Your firewall, CDN, or WAF (web application firewall) is denying or throttling requests from Prerender's crawler IPs.
How to fix it: Whitelist Prerender's IP addresses and crawler user-agent in your firewall, CDN, or WAF configuration. See Prerender IP addresses for the current list.
Cause 2: The Prerender token is missing from your integration
Without a valid token, Prerender's service rejects the request and returns 403.
How to fix it: Add your Prerender token to your integration. You can find your token in your dashboard under Security & Access.
ℹ️ Not sure where your token goes in your specific setup? Ask Nexus, your AI integration assistant inside your Prerender dashboard — describe your stack and Nexus will show you exactly where to place the token.
404 errors: not found
A 404 means Prerender's crawler reached your server, but the URL it requested doesn't resolve to a page. Four causes account for most 404s.
Cause 1: The URL rewrite in your integration is incorrect
Your integration is rewriting incoming crawler URLs to a path that doesn't exist on your site.
How to fix it: Open CDN Analytics in your dashboard to see how the URL was rewritten, then adjust the rewrite section of your integration to produce the correct path.
Cause 2: The requested URL doesn't exist on your site
The crawler is requesting a URL that genuinely isn't there — for example, a page that was removed, never existed, or has a typo in the path.
How to fix it: Confirm the URL exists on your site by loading it in a browser. If the page should exist, fix the broken link or redirect. If it shouldn't, the 404 is expected behavior.
Cause 3: A URL ignore filter matches the requested URL
You have an ignore filter configured that's blocking Prerender from rendering the requested URL.
How to fix it: Check your Ignore URL filters and confirm the requested URL doesn't accidentally match an overly broad pattern. Adjust the filter if needed.
Cause 4: The issue may be URL-specific
The error may only affect one URL or a small set of URLs rather than your whole site.
How to fix it: Test with several other known-valid URLs. If they return 200 and only specific URLs return 404, the problem is isolated to those URLs — check causes 1–3 against the affected paths specifically.
Additional tips and best practices
- Keep your firewall and CDN updated. Update firewall rules to include new IPs or user-agent strings from Prerender when they change.
- Use logs and analytics. Monitor your Prerender dashboard logs, CDN analytics, and server logs to diagnose access problems quickly.
- Avoid overly broad ignore filters. Be precise when setting URL ignore filters to prevent accidentally blocking important pages.
- Validate your integration after changes. Whenever you update your integration or proxy settings, test with known bot user-agents to confirm Prerender is working.
How to verify your fix worked
After applying a fix, test your integration with a crawler user-agent to confirm Prerender now returns rendered HTML instead of an error. Replace www.yourpage.com with your real domain:
curl -v -A googlebot www.yourpage.com/✅ Your fix is working when the response returns a 200 status code with Prerender headers (for example,x-prerender-*) instead of 403 or 404.
For the full verification walkthrough, see How to test your site after integration.
💬 Still need help?
If you've followed the steps above and you're still seeing 403 or 404 errors, our support team can help.
→ Contact us at support@prerender.io
To help us resolve your issue quickly, include the error code you're seeing, the URL affected, any error messages from your dashboard or server logs, and screenshots if available.