SteadyNode

Nginx HTTP 502

What causes an Nginx 502 Bad Gateway?

Troubleshoot Nginx 502 responses by checking upstream availability, proxy configuration, and application logs.

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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Nginx 502: cause and troubleshooting

Nginx could not obtain a valid response from its configured upstream service.

What to check next

Check upstream health and listening sockets, inspect Nginx and application error logs, and verify proxy protocol and TLS settings.

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 does Nginx 502 mean?

Nginx received an invalid response from its upstream or could not connect to that service.

How do I find the source of an Nginx 502?

Correlate Nginx error logs with upstream application logs and verify the configured upstream address and protocol.