← All Status Codes
520
Web Server Error
☁️ Cloudflare
High Risk
📖 What Is HTTP 520?
Cloudflare-specific. The origin server returned an unexpected response that Cloudflare could not process. The origin is reachable but returning invalid data.
🛡️ Security Implications
May indicate the origin server is compromised or misconfigured. Check origin server for unauthorized changes.
🔍 Common Causes
Origin server returning empty response, response headers too large, origin crash mid-response, TCP connection reset.
🔧 How to Fix
Check origin server error logs. Ensure the origin returns valid HTTP responses. Check for header size limits. Restart the origin web server.
🖥️ How to Check
curl -I -o /dev/null -w "%{http_code}" https://example.com