What class of response is HTTP 502?

HTTP 502 is a 5xx Server Error response. These indicate a server-side error.

How do I fix HTTP 502 Bad Gateway?

HTTP 502 is a server error. Check server logs, verify upstream services are running, and ensure your application is not throwing unhandled exceptions.

Is HTTP 502 an error?

Yes, HTTP 502 is an error — specifically a 5xx Server Error code.

HTTP 502 Bad Gateway: What It Means and When You See It

Quick Answer

HTTP 502 Bad Gateway means the server acting as a gateway received an invalid response from an upstream server. Often seen behind reverse proxies.

What HTTP 502 Means

HTTP 502 Bad Gateway means a proxy or gateway server received an invalid, incomplete, or unparseable response from an upstream server. Common in Nginx, AWS ALB, Cloudflare, and API gateways. The error is between the proxy and your backend - the client's request was valid. Common causes: the upstream server returned an invalid HTTP response, the app server crashed mid-response, or the upstream returned a non-HTTP response (port misconfiguration).

Debugging HTTP 502

Check if the upstream service is running: curl localhost:3000 (bypass the proxy). Check proxy error logs - Nginx logs the upstream address that returned the bad response. Common fixes: restart the app server (it may have crashed), check the upstream port and address in proxy config, verify the app is not returning a non-HTTP response on startup, and check for mismatched HTTP versions (proxy uses HTTP/2, upstream only speaks HTTP/1.1).

Try the interactive tool

Convert any value instantly — no sign-up required

Open tool →

Frequently Asked Questions

Related Values

100

HTTP 100 Continue means the server has received the request headers and the client should proceed to send the request body. It is an interim response used to inform the client to continue.

101

HTTP 101 Switching Protocols indicates the server is switching to the protocol specified in the Upgrade header field. Commonly used when upgrading to WebSocket connections.

200

HTTP 200 OK is the standard success response. The request has succeeded and the server has returned the requested resource in the response body.

201

HTTP 201 Created means the request succeeded and a new resource was created as a result. The Location header typically points to the new resource URL.