WebSocket connection fails or drops after about 60 seconds behind Nginx ('WebSocket connection failed', 400/426 or 101 never returned): Upgrade and Connection headers

Cause: Upgrade and Connection are hop-by-hop headers, so nginx does not forward them to the backend unless told to. Without them the backend never sees a WebSocket handshake and the browser connection fails. The handshake also needs HTTP/1.1 to the backend. Separately, nginx closes a proxied connection if the backend sends no data for 60 seconds (the default proxy_read_timeout), which looks like random disconnects on idle sockets. Fix: 1. In the location that serves the socket: proxy_pass http://backend; proxy_http_version 1.1; proxy_set_header Upgrade $http_upgrade; proxy_set_header Connection "upgrade"; (From nginx 1.29.7 onward HTTP/1.1 is the proxy default, so proxy_http_version is only needed on older versions; setting it explicitly is harmless.) 2. If the same location also serves normal HTTP requests, use a map so Connection is only 'upgrade' when the client asked for it: map $http_upgrade $connection_upgrade { default upgrade; '' close; } and then proxy_set_header Connection $connection_upgrade; 3. For idle sockets, either have the application send periodic WebSocket ping frames, or raise proxy_read_timeout for that location (for example 1h). Pings are preferable because they also detect dead peers. 4. Any additional layer (cloud load balancer, CDN, ingress) has its own WebSocket and idle-timeout settings; enable and tune them too. 5. Keep the wss:// URL on the same host and TLS setup as the page to avoid mixed content blocks. Verify: nginx -t and reload succeed; the browser network panel shows the WebSocket request with status 101 and the connection stays open past 60 seconds of idleness (with pings or the raised timeout). Sources: https://nginx.org/en/docs/http/websocket.html https://nginx.org/en/docs/http/ngx_http_proxy_module.html