HTTP 502
Bad Gateway
Server Error
What does "HTTP 502 Bad Gateway" mean?
Plain-English Meaning
A proxy or load balancer got an invalid response from the upstream server. Usually means the backend application crashed or isn't responding.
Common Causes
- Backend application crashed
- PHP-FPM / Node / Python process died
- Deployment mid-swap
- Upstream timeout
- Nginx can't reach backend
What Users Can Do
Reload after 30 seconds — often transient. If persistent, wait for the site owner to fix.
What Developers Can Do
Check backend process status. Look at reverse proxy (nginx/Apache) logs and backend application logs. Verify the backend is bound to the correct port/socket.
Related Status Codes
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