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HTTP Status Code
502 Bad Gateway
Server ErrorThe server received an invalid response from an upstream server.
HTTP status code reference, response example, common causes, fixes, and related status codes.
What does HTTP 502 Bad Gateway mean?
HTTP 502 Bad Gateway is a status code sent by a server to indicate the result of an HTTP request.
Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.
In practice, HTTP 502 Bad Gateway usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.
Response example
HTTP/1.1 502 Bad Gateway
HTTP example
HTTP/1.1 502 Bad Gateway
Common causes
- Reverse proxy error
- Upstream service returned invalid response
- Gateway or load balancer issue
How to fix it
- Check upstream service health
- Inspect proxy and gateway logs
- Verify backend connectivity
Common mistakes
- Assuming the status code alone explains the full backend issue
- Ignoring related response headers that add important context
- Treating temporary errors as permanent failures
- Retrying too aggressively without checking the cause
- Debugging the frontend only when the problem is server-side
How browsers and APIs use it
Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.
Developer note
HTTP 502 usually means your app is not the only layer involved. Check proxies, serverless gateways, CDNs, and upstream APIs.