Server error

502 502 Bad Gateway

A proxy or load balancer could not get a valid response from the application behind it. The front door is fine; whatever it talks to is not.

Common causes

PHP-FPM, Node, Gunicorn or a container has crashed or is not listening.
The upstream is overloaded and refusing connections.
A misconfigured upstream address or port after a deploy.

How to fix it

Check whether the application process is running, and look at its log rather than the proxy log.
Restart the application service, then find out why it died.
Verify the upstream host and port in the proxy configuration.

See what a site actually returns

Run a live check and read the real status code, headers and timings.

Check a website

Other status codes

200 OK 201 Created 204 No Content 206 Partial Content 301 Moved Permanently 302 Found 303 See Other 304 Not Modified 307 Temporary Redirect 308 Permanent Redirect 400 Bad Request 401 Unauthorized 403 Forbidden 404 Not Found 405 Method Not Allowed 408 Request Timeout 410 Gone 413 Payload Too Large 418 I'm a Teapot 429 Too Many Requests 451 Unavailable For Legal Reasons 500 Internal Server Error 501 Not Implemented 503 Service Unavailable 504 Gateway Timeout 507 Insufficient Storage 508 Loop Detected 521 Web Server Is Down 522 Connection Timed Out 523 Origin Is Unreachable 525 SSL Handshake Failed