5xx Server Errors
HTTP 502 Bad Gateway
The server acting as a gateway received an invalid response from an upstream server.
When is 502 used?
- Nginx returning error from upstream
- CDN origin server failure
- API gateway upstream timeout
How to handle a 502 response
The problem is on the server side. Check server and proxy logs, retry idempotent requests with exponential backoff, and alert on sustained 5xx rates.
Check the status code a URL returns from the command line:
curl -s -o /dev/null -w "%{http_code}\n" https://example.comHow to return 502 from your server
Node.js (Express)
res.status(502).json({ message: 'Bad Gateway' });Python (Flask)
return {"message": "Bad Gateway"}, 502Go (net/http)
w.WriteHeader(502)Frequently Asked Questions
What does HTTP 502 mean?
502 Bad Gateway: The server acting as a gateway received an invalid response from an upstream server.
Is 502 an error?
Yes. 502 is in the 5xx Server Errors class. Server errors: the server failed to fulfil an apparently valid request.