What it means

A 502 Bad Gateway response means the server, while acting as a gateway or proxy, received an invalid response from a server it was trying to reach. This is common with reverse proxies and CDNs when the origin server is down or returning malformed responses.

Common causes

• The origin server crashed or is unreachable.
• A reverse proxy like nginx cannot connect to the upstream application server.
• The application server returned an invalid HTTP response.
• A CDN is having trouble reaching its origin.

How to fix it

• If you are a visitor, refresh the page or try again in a few minutes.
• If you are the site owner, check that the upstream application server is running.
• Review proxy configuration and upstream connectivity.
• Check application logs for crashes or errors.