5xx Server errors

502 Bad Gateway

A proxy or load balancer got an invalid answer from the server behind it, for example PHP-FPM crashed or restarted.

Common causes

PHP-FPM or the app process crashed or is restarting.
A proxy (Cloudflare, nginx) cannot reach the origin.
A request that used too much memory and killed the worker.

How to fix a 502 error

1
Check the PHP-FPM / web server error logs and restart the service if you can.
2
Look for memory-heavy requests (large exports, image processing) and move them to a queue.
3
On Cloudflare, check that the origin server is up and the SSL mode is right.

Search error fixes for 502

Check the status of a URL

The first line of the response shows the status code; -L follows redirects and shows each step.

curl -I https://example.com/page
curl -IL https://example.com/old-page

Frequently asked questions

What does HTTP 502 mean?

A proxy or load balancer got an invalid answer from the server behind it, for example PHP-FPM crashed or restarted.

How do I fix a 502 error?

Check the PHP-FPM / web server error logs and restart the service if you can. Look for memory-heavy requests (large exports, image processing) and move them to a queue. On Cloudflare, check that the origin server is up and the SSL mode is right.