CDN Error Explainer
Understand Cloudflare, Akamai, Fastly, and Nginx specific error codes and how to resolve them.
Web Server Returns an Unknown Error
The origin server returned an empty, unknown, or unexpected response to Cloudflare.
How to Fix
Check your origin server logs. Ensure your server is not crashing or returning malformed responses.
Web Server Is Down
The origin server refused the connection from Cloudflare.
How to Fix
Ensure your web server is running. Check firewall rules to allow Cloudflare IPs.
Connection Timed Out
Cloudflare was unable to reach the origin server within the timeout period.
How to Fix
Check origin server load. Verify network connectivity. Increase server timeout if needed.
Origin Is Unreachable
Cloudflare could not reach the origin server due to DNS resolution issues.
How to Fix
Verify DNS records are correct. Check if origin IP is accessible.
A Timeout Occurred
Cloudflare established a TCP connection but the origin did not respond with an HTTP response in time.
How to Fix
Optimize slow database queries. Increase timeout settings. Consider using Cloudflare Workers for long-running tasks.
SSL Handshake Failed
Cloudflare was unable to negotiate an SSL/TLS handshake with the origin server.
How to Fix
Ensure SSL certificate is valid on origin. Check SSL/TLS settings match between Cloudflare and origin.
Invalid SSL Certificate
Cloudflare cannot validate the SSL certificate on the origin web server.
How to Fix
Install a valid SSL certificate on your origin server. Use Full (Strict) SSL mode in Cloudflare.
Railgun Listener to Origin Error
The Railgun connection between Cloudflare and your server failed.
How to Fix
Check Railgun listener status. Verify Railgun configuration.
Origin DNS Error
Cloudflare could not resolve the origin server's hostname.
How to Fix
Verify DNS configuration. Check if the hostname resolves correctly.