SteadyNode

Cloudflare HTTP 520

What does Cloudflare error 520 mean?

Decode Cloudflare error 520, understand why an origin returns an empty or unexpected response, and follow practical steps to troubleshoot it.

Decode a CDN or gateway error

Paste a captured HTTP response or enter a status and headers. Only the status and response headers are sent; common credential headers are filtered first.

Supports raw headers, full HTTP responses, JSON with status/statusCode and headers, cURL -v/-i response output, and HAR exports. HAR selects a server error first. cURL commands are never executed; request headers, response bodies, and common credential headers are excluded.

Find the cause of the next outage sooner

During an outage, every second counts. SteadyNode's uptime engine translates CDN errors into likely root causes on every check.

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Cloudflare 520: cause and troubleshooting

Cloudflare reached the origin, but the origin returned an empty, unknown, or unexpected HTTP response.

What to check next

Check origin application logs for the request time, verify the origin returns a complete HTTP response, and review firewall or proxy rules that may close the connection early.

Use the diagnostic code and provider headers as clues, then confirm the request against origin logs and deployment telemetry. A status code can be generated by a proxy, load balancer, function platform, or origin application; the same number does not always have the same cause across providers.

Keep a CDN error from becoming a long outage

Record the request identifier, timestamp, affected hostname, and deployment when investigating an intermittent failure. SteadyNode checks public endpoints on a schedule and translates recognized upstream errors into concise diagnostic context, helping teams identify whether a failure is at the edge or origin.

Frequently asked questions

What causes Cloudflare error 520?

A 520 usually means the origin sent an empty, malformed, or otherwise unexpected response to Cloudflare.

How do I troubleshoot a 520?

Compare origin logs with the Cloudflare Ray ID, check response headers and connection resets, then test the origin directly from an allowed network.