502 Bad Gateway

The guy behind me fucked up.

What it properly means

The server, acting as a gateway, got an invalid response from the upstream server.

Class
5xx Server error: we fucked up
Defined in
RFC 9110, section 15.6.3

Get one yourself

This endpoint really answers with 502. Point your client at it and see what it does.

curl -i https://httpcodes.dev/api/502

People mix this up with

  • 502504 Gateway Timeout

    Bad answer, or no answer?

    Both come from a proxy or gateway blaming the server behind it. 502 means the upstream replied with rubbish. 504 means it never replied in time.