What the system proxy is: what happens when you flip the switch

When you enable System Proxy on the General page, Clash points the Windows proxy settings (Settings → Network & Internet → Proxy) at its own local listening port, typically 127.0.0.1:7890.

From then on, every program that honors the system proxy sends its traffic to Clash first, and Clash decides per your rules whether to go direct or through a node. Browsers (Chrome, Edge, Firefox) and most chat and office apps belong to this group.

What the system proxy cannot reach

The system proxy is a gentleman's agreement — a program is free to ignore it. Common offenders:

• command-line tools (git, curl, pip, npm — they need their own environment variables);
• most game clients;
• some apps deliberately designed to connect directly.

To force those programs through the proxy, use TUN mode: it works at the network layer and needs no cooperation from the app — see "TUN mode explained".

One more tip: turn the system proxy off before quitting Clash. If Clash exits abnormally and leaves the system proxy pointing at a dead port (symptom: no internet at all), open the Windows proxy settings and switch "Use a proxy server" off to recover.